JBJS | Muscle Performance About the Knee Joint in Patients Who Had Distal Femoral Replacement After Resection of a Bone Tumor : An Objective Study with Use of Gait Analysis*

The Journal of Bone & Joint Surgery, Volume 82, Issue 11

Articles | November 01, 2000

Muscle Performance About the Knee Joint in Patients Who Had Distal Femoral Replacement After Resection of a Bone Tumor : An Objective Study with Use of Gait Analysis*

M. G. Benedetti, M.D.†; F. Catani, M.D.†; D. Donati, M.D.†; L. Simoncini, M.D.†; S. Giannini, M.D.†

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Investigation performed at the Istituti Ortopedici Rizzoli, Bologna, Italy
*No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. No funds were received in support of this study.
†Movement Analysis Laboratory (M. G. B., F. C., L. S., and S. G.) and Bone Tumor Centre (D. D.), Istituti Ortopedici Rizzoli, Via di Barbiano 1/10, 40136 Bologna, Italy. E-mail address for M. G. Benedetti: benedetti@ior.it.

The Journal of Bone & Joint Surgery. 2000; 82:1619-1619

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Abstract

Background: The treatment of a malignant bone tumor in the distal aspect of the femur often requires great sacrifice of bone and muscle. The extent of quadriceps removal has been reported to influence the long-term functional efficiency of a patient's gait. The objective of the present study was to determine gait function as it relates to the residual quadriceps strength and to the specific component or components of the quadriceps removed in patients treated with total knee replacement because of a malignant bone tumor in the distal aspect of the femur.

Methods: Sixteen patients were evaluated after implantation of a modular hinged cementless knee prosthesis. The patients were assigned to two groups on the basis of the different components of the quadriceps muscle that were resected. Group 1 consisted of five patients who had removal of the vastus medialis and the vastus intermedius and two who had removal of the vastus medialis only. Group 2 consisted of nine patients who had removal of the vastus lateralis and the vastus intermedius. Residual muscular strength about the treated knee was measured by voluntary maximum contraction isometric testing. Foot-ground reaction forces, kinematic and kinetic findings, and electromyographic activity during free-speed walking were recorded.

Results: The kinematic study showed that the patients in Group 1 tended to have a stiff-knee gait during stance, whereas those in Group 2 (in which the vastus medialis was spared) had a more regular flexion-extension knee pattern. Electromyographic findings showed that a higher percentage of patients in Group 1 had reduced or absent rectus femoris activity during the loading response. Compared with the contralateral side, knee-extension strength in the treated limb was decreased in both groups. However, there were no significant differences between the groups with respect to the pattern of strength loss.

Conclusions: Good gait function can be achieved in patients with a distal femoral tumor that is treated with distal femoral resection, partial excision of the quadriceps, and total knee arthroplasty with insertion of a hinged prosthesis. Patients in whom the vastus lateralis and vastus intermedius were removed had better gait performance and a more physiological knee-loading pattern than did patients in whom the vastus medialis was removed.

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Introduction

Introduction | Materials and Methods | Results | Discussion | References

The operative treatment of a malignant bone tumor in the distal part of the femur presents a complex problem to the surgeon. While the resection has to be wide enough to avoid local recurrence, the best possible limb function is obtained by a minimal amount of tissue resection^3,10. Whenever possible, knee mobility should be preserved. This goal is best achieved in the long term with a cementless total knee prosthesis^4,11. Because of the need to remove part or all of the quadriceps, a hinged, fully constrained prosthesis usually is chosen to provide mechanical stability⁵. Depending upon the location and the extent of the tumor, a medial, a lateral, or a combined operative approach is used¹⁵. A major clinical concern is the long-term functional efficiency of the patient's gait and its possible influence on implant failure^9,13,16,17. Previous studies have demonstrated that the extent of quadriceps removal affects the strength of active knee extension; however, no particular pattern of strength reduction could be discerned relative to the specific part or parts of the quadriceps that were removed¹². Satisfactory functional results have been reported after limited or subtotal excision of the quadriceps, but extensor power has been found to be substantially decreased when more than two heads of the quadriceps are resected⁵. In an experimental study based on a mathematical model, van Krieken et al. concluded that partial excision of the quadriceps allowed normal gait, whereas complete excision and prosthetic instability resulted in major changes in gait pattern and high joint loads¹⁸. On the basis of these reports, we hypothesized that the quality of the resulting gait of patients who have had resection of a malignant tumor and total knee replacement depends on the residual extensor strength rather than on the pattern of muscle removal.

The goal of our study was to determine the level of locomotor function as it relates both to the specific component or components of the quadriceps muscle removed and to the residual quadriceps strength in patients who had been treated because of a malignant bone tumor in the distal part of the femur.

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Fig. 1:: Graphs showing the gait parameters measured. BW = body weight, and H = height.

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TABLE I: Data on the Patients

Case	Gender, Age (yrs.)	Duration of Follow-up (mos.)	Diagnosis	Side	Type of Excision	Patella	Length of Resection (cm)	Quadriceps Heads Excised	Functional Score
Group 1
1	M, 25	44	Osteogenic sarcoma	R	Extra-articular	Partially removed	14	Vastus medialis and vastus intermedius	Good
2	M, 23	38	Malignant fibrohistio-cytoma	L	Intra-articular	Not removed	16	Vastus medialis	Good
3	M, 29	37	Osteogenic sarcoma	L	Intra-articular	Not removed	16	Vastus medialis and vastus intermedius	Good
4	M, 26	44	Osteogenic sarcoma	R	Intra-articular	Not removed	16	Vastus medialis	Excellent
5	M, 18	23	Osteogenic sarcoma	R	Intra-articular	Not removed	20	Vastus medialis and vastus intermedius	Excellent
6	M, 22	55	Osteogenic sarcoma	L	Intra-articular	Not removed	20	Vastus medialis and vastus intermedius	Excellent
7	F, 30	22	Osteogenic sarcoma	L	Intra-articular	Not removed	12	Vastus medialis and vastus intermedius	Good
Group 2
8	M, 51	48	Fibro- sarcoma	L	Extra-articular	Partially removed	16	Vastus lateralis and vastus intermedius	Good
9	F, 27	36	Osteogenic sarcoma	R	Extra-articular	Partially removed	18	Vastus lateralis and vastus intermedius	Good
10	F, 40	68	Osteogenic sarcoma	L	Intra-articular	Not removed	14	Vastus lateralis and vastus intermedius	Good
11	M, 40	33	Malignant fibrohistio-cytoma	R	Intra-articular	Not removed	18	Vastus lateralis and vastus intermedius	Good
12	M, 24	104	Osteogenic sarcoma	R	Intra-articular	Not removed	18	Vastus lateralis and vastus intermedius	Excellent
13	M, 50	34	Osteogenic sarcoma	R	Intra-articular	Not removed	14	Vastus lateralis and vastus intermedius	Good
14	M, 20	53	Osteogenic sarcoma	R	Intra-articular	Not removed	18	Vastus lateralis and vastus intermedius	Excellent
15	F, 19	35	Osteogenic sarcoma	R	Intra-articular	Not removed	16	Vastus lateralis and vastus intermedius	Excellent
16	M, 20	22	Osteogenic sarcoma	L	Intra-articular	Not removed	20	Vastus lateralis and vastus intermedius	Excellent

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TABLE I: Data on the Patients

Case	Gender, Age (yrs.)	Duration of Follow-up (mos.)	Diagnosis	Side	Type of Excision	Patella	Length of Resection (cm)	Quadriceps Heads Excised	Functional Score
Group 1
1	M, 25	44	Osteogenic sarcoma	R	Extra-articular	Partially removed	14	Vastus medialis and vastus intermedius	Good
2	M, 23	38	Malignant fibrohistio-cytoma	L	Intra-articular	Not removed	16	Vastus medialis	Good
3	M, 29	37	Osteogenic sarcoma	L	Intra-articular	Not removed	16	Vastus medialis and vastus intermedius	Good
4	M, 26	44	Osteogenic sarcoma	R	Intra-articular	Not removed	16	Vastus medialis	Excellent
5	M, 18	23	Osteogenic sarcoma	R	Intra-articular	Not removed	20	Vastus medialis and vastus intermedius	Excellent
6	M, 22	55	Osteogenic sarcoma	L	Intra-articular	Not removed	20	Vastus medialis and vastus intermedius	Excellent
7	F, 30	22	Osteogenic sarcoma	L	Intra-articular	Not removed	12	Vastus medialis and vastus intermedius	Good
Group 2
8	M, 51	48	Fibro- sarcoma	L	Extra-articular	Partially removed	16	Vastus lateralis and vastus intermedius	Good
9	F, 27	36	Osteogenic sarcoma	R	Extra-articular	Partially removed	18	Vastus lateralis and vastus intermedius	Good
10	F, 40	68	Osteogenic sarcoma	L	Intra-articular	Not removed	14	Vastus lateralis and vastus intermedius	Good
11	M, 40	33	Malignant fibrohistio-cytoma	R	Intra-articular	Not removed	18	Vastus lateralis and vastus intermedius	Good
12	M, 24	104	Osteogenic sarcoma	R	Intra-articular	Not removed	18	Vastus lateralis and vastus intermedius	Excellent
13	M, 50	34	Osteogenic sarcoma	R	Intra-articular	Not removed	14	Vastus lateralis and vastus intermedius	Good
14	M, 20	53	Osteogenic sarcoma	R	Intra-articular	Not removed	18	Vastus lateralis and vastus intermedius	Excellent
15	F, 19	35	Osteogenic sarcoma	R	Intra-articular	Not removed	16	Vastus lateralis and vastus intermedius	Excellent
16	M, 20	22	Osteogenic sarcoma	L	Intra-articular	Not removed	20	Vastus lateralis and vastus intermedius	Excellent

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TABLE II: Difference Between the Treated and the Contralateral Knee with Respect to Extensor Peak Torque on Isometric Muscle-Strength Testing

*The values are given as the mean and the standard deviation.†According to analysis of variance. NS = not significant.‡According to the Mann-Whitney U test.

Knee Angle (degrees)	Group 1* (Medial) (percent)	Group 2* (Lateral) (percent)	P Value†
90	-79.7 ± 9.9	-75.8 ± 11.4	NS
60	-74.3 ± 9.2	-65.4 ± 13.7	NS
30	-58.6 ± 17.4	-43.6 ± 22.2	NS
0	-33.6 ± 32.4	-39.8 ± 20.2	NS‡

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TABLE II: Difference Between the Treated and the Contralateral Knee with Respect to Extensor Peak Torque on Isometric Muscle-Strength Testing

*The values are given as the mean and the standard deviation.†According to analysis of variance. NS = not significant.‡According to the Mann-Whitney U test.

Knee Angle (degrees)	Group 1* (Medial) (percent)	Group 2* (Lateral) (percent)	P Value†
90	-79.7 ± 9.9	-75.8 ± 11.4	NS
60	-74.3 ± 9.2	-65.4 ± 13.7	NS
30	-58.6 ± 17.4	-43.6 ± 22.2	NS
0	-33.6 ± 32.4	-39.8 ± 20.2	NS‡

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TABLE III: Gait-Analysis Data

*According to analysis of variance unless otherwise indicated. NS = not significant.†The values are given as the mean and the standard deviation.‡According to the Kruskal-Wallis test. NS = not significant.Â§Calculated as the percent of body weight times height.

	P Value*	Control Group†	Group 1† (Medial)	Group 2† (Lateral)	P Value According to Scheffé F Test
Control Group Compared with Group 1	Control Group Compared with Group 2	Group 1 Compared with Group 2
Time-distance parameters
Stance phase (percent of stride)	NS	60.4 ± 2.0	59.8 ± 1.4	60.9 ± 1.8	NS	NS	NS
Stride length (percent of height)	0.01‡	83.3 ± 7.5	79.9 ± 5.5	80 ± 9.9	0.05	NS	NS
Cycle time (secs.)	0.001‡	1.12 ± 0.09	1.19 ± 0.08	1.17 ± 0.1	0.01	0.03	NS
Cadence (stride/min.)	0.001	53.9 ± 4.2	50.6 ± 3.4	51.15 ± 4.2	0.006	0.03	NS
Speed of progression (cm/sec.)	0.002	125.6 ± 16.8	115.4 ± 13.6	115.2 ± 17.1	0.035	0.015	NS
Ground-reaction forces (percent of body weight)
F1	<0.0001	112 ± 8.9	100.4 ± 7.4	97.3 ± 4.4	<0.0001	<0.0001	NS
F2	<0.0001	73 ± 6.8	80.6 ± 4.4	81.1 ± 5.9	<0.0001	<0.0001	NS
F3	<0.0001	114 ± 6.5	101.3 ± 5.9	106 ± 5.9	<0.0001	<0.0001	NS
F4	0.018‡	4.5 ± 3.4	2.5 ± 2	2.9 ± 2.4	0.003	NS	NS
F5	<0.0001‡	-19.3 ± 4.2	-16.8 ± 4.8	-14.8 ± 2.5	<0.0001	<0.0001	NS
F6	<0.0001	21.7 ± 4.3	18.4 ± 2.8	17.4 ± 3.3	<0.0001	<0.0001	NS
F7	<0.0001	-4.7 ± 2.0	-2.1 ± 2.3	-2.7 ± 1.7	<0.0001	<0.0001	NS
F8	NS‡	6.6 ± 1.3	6 ± 1.4	6 ± 1.4	NS	NS	NS
F9	0.003‡	5.5 ± 1.9	7 ± 1.7	5.7 ± 1.2	0.004	NS	0.02
Knee-angle parameters (degrees)
K1	NS	0.4 ± 4.8	0.5 ± 3.8	2.3 ± 5.3	NS	NS	NS
K2	<0.0001	17.9 ± 7.6	5.7 ± 5.7	11.1 ± 7.9	<0.0001	<0.0001	0.049
K3	NS	4.9 ± 4.5	3.9 ± 4.6	6.8 ± 6.7	NS	NS	NS
K4	0.002	36.6 ± 7.6	42.6 ± 7.1	39.6 ± 7.5	0.004	NS	NS
K5	NS	65.6 ± 5.2	65.4 ± 5.1	65.6 ± 8.7	NS	NS	NS
K6	NS	60.7 ± 5.1	61.4 ± 8.7	58.7 ± 11.8	NS	NS	NS
External knee moment parametersÂ§
KM1	<0.0001‡	-4.2 ± 1.3	-3.1 ± 0.8	-3.4 ± 0.9	<0.0001	0.02	NS
KM2	<0.0001‡	1.4 ± 2.0	-0.6 ± 0.9	-0.5 ± 1.5	<0.0001	<0.0001	NS
KM3	0.0001‡	-2.7 ± 1.4	-1.7 ± 0.9	-1.9 ± 1.9	<0.0001	NS	<0.0001
KM4	0.001	1 ± 0.6	0.8 ± 0.5	0.5 ± 0.5	NS	0.001	NS
KM5	<0.0001	-2.3 ± 1.1	-1.1 ± 0.5	-1.9 ± 0.7	<0.0001	NS	NS
KM6	0.001‡	-1.6 ± 1.0	-0.9 ± 0.6	-1.9 ± 0.5	<0.0001	NS	<0.0001
KM7	NS‡	-0.24 ± 0.41	-0.3 ± 0.18	-0.11 ± 0.14	NS	NS	NS
KM8	0.0004	1 ± 0.45	0.7 ± 0.25	0.9 ± 0.42	0.021	NS	NS

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TABLE III: Gait-Analysis Data

	P Value*	Control Group†	Group 1† (Medial)	Group 2† (Lateral)	P Value According to Scheffé F Test
Control Group Compared with Group 1	Control Group Compared with Group 2	Group 1 Compared with Group 2
Time-distance parameters
Stance phase (percent of stride)	NS	60.4 ± 2.0	59.8 ± 1.4	60.9 ± 1.8	NS	NS	NS
Stride length (percent of height)	0.01‡	83.3 ± 7.5	79.9 ± 5.5	80 ± 9.9	0.05	NS	NS
Cycle time (secs.)	0.001‡	1.12 ± 0.09	1.19 ± 0.08	1.17 ± 0.1	0.01	0.03	NS
Cadence (stride/min.)	0.001	53.9 ± 4.2	50.6 ± 3.4	51.15 ± 4.2	0.006	0.03	NS
Speed of progression (cm/sec.)	0.002	125.6 ± 16.8	115.4 ± 13.6	115.2 ± 17.1	0.035	0.015	NS
Ground-reaction forces (percent of body weight)
F1	<0.0001	112 ± 8.9	100.4 ± 7.4	97.3 ± 4.4	<0.0001	<0.0001	NS
F2	<0.0001	73 ± 6.8	80.6 ± 4.4	81.1 ± 5.9	<0.0001	<0.0001	NS
F3	<0.0001	114 ± 6.5	101.3 ± 5.9	106 ± 5.9	<0.0001	<0.0001	NS
F4	0.018‡	4.5 ± 3.4	2.5 ± 2	2.9 ± 2.4	0.003	NS	NS
F5	<0.0001‡	-19.3 ± 4.2	-16.8 ± 4.8	-14.8 ± 2.5	<0.0001	<0.0001	NS
F6	<0.0001	21.7 ± 4.3	18.4 ± 2.8	17.4 ± 3.3	<0.0001	<0.0001	NS
F7	<0.0001	-4.7 ± 2.0	-2.1 ± 2.3	-2.7 ± 1.7	<0.0001	<0.0001	NS
F8	NS‡	6.6 ± 1.3	6 ± 1.4	6 ± 1.4	NS	NS	NS
F9	0.003‡	5.5 ± 1.9	7 ± 1.7	5.7 ± 1.2	0.004	NS	0.02
Knee-angle parameters (degrees)
K1	NS	0.4 ± 4.8	0.5 ± 3.8	2.3 ± 5.3	NS	NS	NS
K2	<0.0001	17.9 ± 7.6	5.7 ± 5.7	11.1 ± 7.9	<0.0001	<0.0001	0.049
K3	NS	4.9 ± 4.5	3.9 ± 4.6	6.8 ± 6.7	NS	NS	NS
K4	0.002	36.6 ± 7.6	42.6 ± 7.1	39.6 ± 7.5	0.004	NS	NS
K5	NS	65.6 ± 5.2	65.4 ± 5.1	65.6 ± 8.7	NS	NS	NS
K6	NS	60.7 ± 5.1	61.4 ± 8.7	58.7 ± 11.8	NS	NS	NS
External knee moment parametersÂ§
KM1	<0.0001‡	-4.2 ± 1.3	-3.1 ± 0.8	-3.4 ± 0.9	<0.0001	0.02	NS
KM2	<0.0001‡	1.4 ± 2.0	-0.6 ± 0.9	-0.5 ± 1.5	<0.0001	<0.0001	NS
KM3	0.0001‡	-2.7 ± 1.4	-1.7 ± 0.9	-1.9 ± 1.9	<0.0001	NS	<0.0001
KM4	0.001	1 ± 0.6	0.8 ± 0.5	0.5 ± 0.5	NS	0.001	NS
KM5	<0.0001	-2.3 ± 1.1	-1.1 ± 0.5	-1.9 ± 0.7	<0.0001	NS	NS
KM6	0.001‡	-1.6 ± 1.0	-0.9 ± 0.6	-1.9 ± 0.5	<0.0001	NS	<0.0001
KM7	NS‡	-0.24 ± 0.41	-0.3 ± 0.18	-0.11 ± 0.14	NS	NS	NS
KM8	0.0004	1 ± 0.45	0.7 ± 0.25	0.9 ± 0.42	0.021	NS	NS

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TABLE IV: Present or Prolonged Activity of the Rectus Femoris During Stance Phase*

*The difference between Group 1 and Group 2 was found to be significant (Fisher exact test, p = 0.018).

	Group 1 (Medial)	Group 2 (Lateral)	Total
No. (percent) of gait trials with activity	9 (43)	21 (78)	30 (63)
No. (percent) of gait trials with reduced or absent activity	12 (57)	6 (22)	18 (38)
Total no. (percent) of gait trials	21 (100)	27 (100)	48 (100)

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TABLE IV: Present or Prolonged Activity of the Rectus Femoris During Stance Phase*

*The difference between Group 1 and Group 2 was found to be significant (Fisher exact test, p = 0.018).

	Group 1 (Medial)	Group 2 (Lateral)	Total
No. (percent) of gait trials with activity	9 (43)	21 (78)	30 (63)
No. (percent) of gait trials with reduced or absent activity	12 (57)	6 (22)	18 (38)
Total no. (percent) of gait trials	21 (100)	27 (100)	48 (100)

Materials and Methods

Introduction | Materials and Methods | Results | Discussion | References

Sixteen patients previously managed with an operation because of a high-grade bone sarcoma in the distal part of the femur were evaluated at a mean of forty-four months (range, twenty-two to 104 months) postoperatively (Table I). The resection was intra-articular in thirteen patients and extra-articular in three. In the latter three patients, the patella was partially removed, but its quadriceps tendon insertion was preserved. The surgical approach depended upon the tumor site. A medial approach was used in seven patients (Group 1), and a lateral approach was used in nine (Group 2). In two patients in Group 1, only the vastus medialis was removed; in five patients in Group 1, both the vastus medialis and the vastus intermedius were removed. In all nine patients in Group 2, the vastus lateralis and the vastus intermedius were removed. The amount of bone resection varied according to the extent of the tumor and ranged from twelve to twenty centimeters, as measured from the joint line. In all patients, the distal part of the femur was surgically reconstructed with use of a modular, hinged cementless prosthesis (KMFTR [Kotz Modular Femur and Tibia Reconstruction system]; Howmedica, Rutherford, New Jersey)¹¹, which is fully constrained and intrinsically stable. At terminal extension, it allows recurvatum of about 6 degrees, providing stability of the knee by passive hyperextension. It has 8 degrees of valgus alignment to reproduce the correct mechanical axis and to allow physiological axial joint-loading.

Eleven complications occurred during the follow-up period. Broken screws were noted in the proximal part of the stem (without revision) in five patients, and varus-valgus loosening developed in six patients because of wear of the polyethylene bushings. All six subsequently underwent revision of the worn bushings. At the time of gait analysis, varus-valgus instability of the prosthesis was not clinically evident in any patient.

The evaluation system of the Musculoskeletal Tumor Society^7,8 was used to assess functional outcome. Anteroposterior and lateral radiographs, made at the time of gait analysis, were reviewed to evaluate prosthetic alignment and stability.

Muscular strength at the knee was measured by voluntary maximum contraction isometric testing with use of a dynamometer (REV 9000; Technogym, Gambettola, Italy). The test consisted of measurement of the maximum extension moment with the knee in 90, 60, 30, and 0 degrees of flexion. The test was performed on both the treated limb and the healthy limb, and the percentage difference between the two limbs with respect to the residual extensor peak torque was calculated. Isometric testing data were also analyzed by means of one-way analysis of variance (p < 0.01), with use of a Mann-Whitney nonparametric U test (p < 0.05) when the Levene test for uniformity of variances showed a significant difference (p < 0.05). Knee performance during free-speed walking was evaluated by means of a stereophotogrammetric system for the acquisition of kinematic variables (Elite; BTS, Milan, Italy). Foot-ground reaction forces were recorded with use of two Kistler force-plates (Kistler Instrumente, Winterthur, Switzerland). On the basis of kinematic and force data, external joint moments were calculated².

Kinematic and kinetic evaluation was performed with the Calibrated Anatomical System Technique⁶. An eight-channel electromyographic telemetry system (TELEMG; BTS, Milan, Italy) was used to record the surface electromyographic signal from the right and left longissimus dorsi, gluteus medius, rectus femoris, medial and lateral hamstring, gastrocnemius, and tibialis anterior muscles. The myoelectrical signals were acquired simultaneously with the kinematic and kinetic data. The phasic activity of the muscles was determined by visual inspection of the electromyographic signal and was compared with data reported in the literature¹⁴. Contingency tables (p < 0.05) were used to analyze the frequency with which any changes in muscular activity occurred.

According to the methodology described in our previous study², clinically relevant parameters were obtained at particular instants during the gait cycle (Fig. 1). Because the prosthesis was hinged, we considered only parameters of movement in the sagittal plane. Three gait trials were recorded for each patient. The mean scores were compared with data from a control group of ten healthy subjects.

Gait parameters from Group 1, Group 2, and the control group were compared by means of one-way analysis of variance (p < 0.01), when the Levene test (p < 0.05) for uniformity of variances was not significant. Otherwise, the Kruskal-Wallis nonparametric test was used. The post hoc Scheffç?? test (p < 0.05) was used for pairwise multiple comparisons among groups. The SPSS statistical package (SPSS, Chicago, Illinois) was used for all statistical analysis methods.

Results

Introduction | Materials and Methods | Results | Discussion | References

Clinical Evaluation and Radiographic Assessment

No significant differences between Group 1 and Group 2 were found with respect to age (mean, 25 ± 3.8 years for Group 1 and 32 ± 12 years for Group 2), duration of follow-up (mean, 37.6 ± 19.6 months for Group 1 and 48.1 ± 25 months for Group 2), or length of bone resection (mean, 16.3 ± 2.8 centimeters for Group 1 and 16.9 ± 1.9 centimeters for Group 2). No gross radiographic abnormalities were noted in any of the patients. On the basis of the radiographic and clinical results, the prostheses were judged to be stable. The clinical result was excellent in seven patients and good in nine. The excellent and good results were distributed evenly between the two groups.

Muscle Strength

The percentage difference in peak torque of the extensor apparatus of the treated limb compared with that in the contralateral limb was measured during isometric contraction with the knee in 90, 60, 30, and 0 degrees of flexion (Table II). The reduction of the knee extensor strength was greater in the more flexed positions of the knee (60 and 90 degrees). With the number of patients in the present study, no difference between the two groups was found with respect to quadriceps muscle strength.

Gait Analysis

Time-Distance Parameters

A reduced stride length (p = 0.01), a longer cycle time (p = 0.001), and a consequent reduction in speed of progression (p = 0.002) (Table III) were seen in both groups. Group 1 demonstrated a slightly but significantly reduced stride length compared with that in the control group (p = 0.05).

Foot-Ground Reaction Forces

All ground-reaction force parameters except F8 were altered (p < 0.05) (Table III). In contrast to the patients in Group 2, those in Group 1 had a significantly lower fore-aft force peak (F4) in the loading-response phase (p = 0.003) and an increased medial-lateral push-off component (F9) during the terminal stance phase (p = 0.004) compared with those in the controls.

Kinematics of the Treated Knee

A significant difference between both groups and the controls was found with respect to the load-absorption parameter (K2) (p < 0.0001). The decrease in knee flexion with respect to that in the control group (mean, 17.9 ± 7.6 degrees) was much greater in Group 1 (mean, 5.7 ± 5.7 degrees) (p < 0.0001) than in Group 2 (mean, 11.1 ± 7.9 degrees) (p < 0.0001). At toe-off (K4), on the average the knee was flexed more in all patients (p = 0.002), particularly those in Group 1, than it was in the control group (p = 0.004). In general, knee flexion after heel-strike was reduced in the patients in Group 1 (compared with those in Group 2), and the gait could be characterized as more "stiff-kneed" in the loading-response and midstance phases (K2) (p = 0.049). The knee then unlocked and reached more flexion at toe-off (K4).

External Joint Moments at the Knee

A significant reduction was detected in the external joint moments at the knee for most of the considered parameters in both groups compared with those in the controls (Table III). A decrease in the extension moment (KM1) as well as in the flexion moment (KM2) was evident in both groups (p < 0.0001). The second peak extension moment (KM3) (p = 0.0001) was decreased, with a significant reduction in Group 1 compared with Group 2 (p < 0.0001). In the coronal and the transverse plane, there was a greater tendency to keep the resultant force vector very close to the center of joint rotation. The Scheffç?´est revealed that, while there was a more reduced abduction moment (KM4) in Group 2 (p = 0.001), Group 1 had a greater reduction in the adduction moment peaks (KM5 and KM6) (p < 0.0001). Finally, in the transverse plane, a significant reduction in the internal rotation moment (KM8) was seen in the patients in Group 1 (p = 0.021).

Dynamic Electromyography

Dynamic electromyography demonstrated reduced or absent activity of the rectus femoris during the stance phase in 57 percent (twelve) of the twenty-one Group-1 trials but in only 22 percent (six) of the twenty-seven Group-2 trials (Table IV). This difference was significant (Fisher exact test, p = 0.018). No differences were found in the timing of activation of other muscles tested.

Discussion

Introduction | Materials and Methods | Results | Discussion | References

Patients with a malignant tumor in the distal aspect of the femur undergo the excision of a large amount of bone and muscle to ensure complete removal of the tumor and to reduce the risk of local recurrence. We suspected that resecting a large portion of the quadriceps would cause a major alteration in gait after total knee replacement, leading to failure of the prosthesis.

While the functional outcome assessment score was excellent or good for all of our patients, we found slight differences in gait biomechanics depending upon which heads of the quadriceps had been excised. The patients in Group 2, who had removal of the vastus intermedius and vastus lateralis, had less significant gait deviations than did those in Group 1. The variation in the time-distance parameters highlighted the fact that all of the patients had a slow gait. While some of the changes in the ground-reaction force pattern could have been associated with the reduction in speed¹, some seem to have been related to the specific muscles excised. In particular, Group-1 patients had greater gait deviations both in the loading-response phase, characterized by an initial forward-directed limb-loading pattern, and in medial-lateral push-off in the propulsive phase.

The kinematic study showed that Group-1 patients tended to have a stiff-knee gait during stance, while Group-2 patients had a more normal knee flexion-extension load-absorption pattern. This finding was supported by electromyographic data, which showed that a higher percentage of patients in Group 1 had reduced or absent rectus femoris activity during the loading-response phase (when such activity is normally present¹⁴), suggesting a mechanical stabilization pattern of the prosthesis.

Our findings did not support our hypothesis that residual isometric extensor mechanism strength would be positively associated with better biomechanical patterns of gait. Isometric knee-extension strength was decreased in the treated limb compared with that in the contralateral limb in both groups, but no significant differences were seen between Group 1 and Group 2 with respect to the degree of strength loss. According to the literature¹², greater knee-extensor deficits have been found in the more flexed positions of the knee (60 and 90 degrees). If the strength of the residual quadriceps was not the discriminating factor between the two groups and the knee stability was ensured by the mechanical structure of the prosthesis, other factors, such as the muscles removed, may be an important influence upon gait performance.

In conclusion, our findings suggest that implantation of a hinged total knee prosthesis after excision of a distal femoral tumor with removal of one or two of the quadriceps muscles provides good functional results during gait. Patients with excision of the vastus lateralis and vastus intermedius show a gait pattern that is closer to normal. While the decision regarding the amount of quadriceps to be excised must be determined by the extent of the malignant lesion, preservation of the vastus medialis seems to enhance motor control of the knee. Additional studies should be performed to evaluate the relationship between the number and extent of the quadriceps heads excised and both the knee mechanics during gait and the long-term survival of the prosthesis.

Note: We thank E. Pignotti, Eng. (Istituti Ortopedici Rizzoli, Bologna, Italy) for providing professional assistance with the statistical analysis.

References

Introduction | Materials and Methods | Results | Discussion | References

Andriacchi, T. P.; Ogle, J. A.; and Galante, J. O.: Walking speed as a basis for normal and abnormal gait measurement. J. Biomech.,10: 261-268, 1977.10261 1977 [PubMed]

Benedetti, M. G.; Catani, F.; Leardini, A.; Pignotti, E.; and Giannini, S.: Data management in gait analysis for clinical applications. Clin. Biomech.,13: 204-215, 1998.13204 1998

Campanacci, M. Bone and Soft Tissue Tumors, pp. 43-70. New York, Springer, 1990

Capanna, R.; Leonessa, C.; Betelli, G.; Borghi, B.; deCristofaro, R.; Martelli, C.; Ruggieri, P.; and Campanacci, M. Modular Kotz prosthesis. The Rizzoli experience. In New Developments for Limb Salvage in Musculoskeletal Tumors. Kyocera Orthopaedic Symposium, pp. 37-44. Edited by T. Yamamuro. New York, Springer, 1989.

Capanna, R.; Ruggieri, P.; Biagini, R.; Ferraro, A.; DeCristofaro, R.; McDonald, D.; and Campanacci, M.: The effect of quadriceps excision on functional results after distal femoral resection and prosthetic replacement of bone tumors. Clin. Orthop.,267: 186-196, 1991.267186 1991 [PubMed]

Cappozzo, A.; Catani, F.; Della Croce, U.; and Leardini, A.: Position and orientation in space of bones during movement: anatomical frame definition and determination. Clin. Biomech.,10: 171-178, 1995.10171 1995

Enneking, W. F. Modified system for functional evaluation of surgical management of musculoskeletal tumors. In Limb Salvage. Musculoskeletal Oncology, pp. 625-640. Edited by W. F. Enneking. New York, Churchill Livingstone, 1987

Enneking, W. F.; Dunham, W.; Gebhardt, M. C.; Malawar, M. W.; and Pritchard, D. J.: A system for the functional evaluation of reconstructive procedures after surgical treatment of tumors of the musculoskeletal system. Clin. Orthop.,286: 241-246, 1993.286241 1993 [PubMed]

Kawai, A.; Backus, S. I.; Otis, J. C.; and Healey, J. H.: Interrelationships of clinical outcome, length of resection, and energy cost of walking after prosthetic knee replacement following resection of a malignant tumor of the distal aspect of the femur. J. Bone and Joint Surg.,80-A: 822-831, June 1998.80-A822 1998

Klein, M. J.; Kenan, S.; and Lewis, M. M.: Osteosarcoma. Clinical and pathological considerations. Orthop. Clin. North America,20: 327-345, 1989.20327 1989

Kotz, R.; Ritschl, P.; and Trachtenbrodt, J.: A modular femur-tibia reconstruction system. Orthopedics,9: 1639-1652, 1986.91639 1986 [PubMed]

Markhede, G., and Stener, B.: Function after removal of various hip and thigh muscles for extirpation of tumors. Acta Orthop. Scandinavica,,52: 373-395, 1981.52373 1981

Otis, J. C.; Backus, S. L.; Barr, A. E.; Peterson, M. G.; and Dayan, A. J. Quantitative assessment of patient performance after major limb reconstruction. In Proceedings of the Sixth International Symposium on Limb Salvage (ISOLS), pp. 25-31. Edited by K. L. B. Brown. Montreal, International Symposium on Limb Salvage, 1991.

Perry, J. Gait Analysis. Normal and Pathological Function. Thorofare, New Jersey, Slack, 1992.

Simon, M. A. and Springfield, D. [editors]: Surgery for Bone and Soft-Tissue Tumors. Philadelphia, Lippincott-Raven, 1998.

Suzuki, R.; Hirano, T.; Fujita, M.; and Matsusaka, N. Gait analysis in patients with osteosarcoma treated by limb salvage procedures. In New Developments for Limb Salvage in Musculoskeletal Tumors. Kyocera Orthopaedic Symposium, pp. 9-16. Edited by T. Yamamuro. New York, Springer, 1989.

Tsuboyama, T.; Windhager, R.; Bochdansky, T.; Yamamuro, T.; and Kotz, R.: Gait after knee arthroplasty for femoral tumor. Acta Orthop. Scandinavica,65: 51-54, 1994.6551 1994

van Krieken, F. M.; den Heeten, G. J.; Pedersen, D. R.; Brand, R. A.; and Crowninshield, R. D.: Prediction of muscle and joint loads after segmental femur replacement for osteosarcoma. Clin. Orthop.,198: 273-283, 1985.198273 1985 [PubMed]

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Fig. 1:: Graphs showing the gait parameters measured. BW = body weight, and H = height.

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TABLE I: Data on the Patients

Case	Gender, Age (yrs.)	Duration of Follow-up (mos.)	Diagnosis	Side	Type of Excision	Patella	Length of Resection (cm)	Quadriceps Heads Excised	Functional Score
Group 1
1	M, 25	44	Osteogenic sarcoma	R	Extra-articular	Partially removed	14	Vastus medialis and vastus intermedius	Good
2	M, 23	38	Malignant fibrohistio-cytoma	L	Intra-articular	Not removed	16	Vastus medialis	Good
3	M, 29	37	Osteogenic sarcoma	L	Intra-articular	Not removed	16	Vastus medialis and vastus intermedius	Good
4	M, 26	44	Osteogenic sarcoma	R	Intra-articular	Not removed	16	Vastus medialis	Excellent
5	M, 18	23	Osteogenic sarcoma	R	Intra-articular	Not removed	20	Vastus medialis and vastus intermedius	Excellent
6	M, 22	55	Osteogenic sarcoma	L	Intra-articular	Not removed	20	Vastus medialis and vastus intermedius	Excellent
7	F, 30	22	Osteogenic sarcoma	L	Intra-articular	Not removed	12	Vastus medialis and vastus intermedius	Good
Group 2
8	M, 51	48	Fibro- sarcoma	L	Extra-articular	Partially removed	16	Vastus lateralis and vastus intermedius	Good
9	F, 27	36	Osteogenic sarcoma	R	Extra-articular	Partially removed	18	Vastus lateralis and vastus intermedius	Good
10	F, 40	68	Osteogenic sarcoma	L	Intra-articular	Not removed	14	Vastus lateralis and vastus intermedius	Good
11	M, 40	33	Malignant fibrohistio-cytoma	R	Intra-articular	Not removed	18	Vastus lateralis and vastus intermedius	Good
12	M, 24	104	Osteogenic sarcoma	R	Intra-articular	Not removed	18	Vastus lateralis and vastus intermedius	Excellent
13	M, 50	34	Osteogenic sarcoma	R	Intra-articular	Not removed	14	Vastus lateralis and vastus intermedius	Good
14	M, 20	53	Osteogenic sarcoma	R	Intra-articular	Not removed	18	Vastus lateralis and vastus intermedius	Excellent
15	F, 19	35	Osteogenic sarcoma	R	Intra-articular	Not removed	16	Vastus lateralis and vastus intermedius	Excellent
16	M, 20	22	Osteogenic sarcoma	L	Intra-articular	Not removed	20	Vastus lateralis and vastus intermedius	Excellent

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TABLE I: Data on the Patients

Case	Gender, Age (yrs.)	Duration of Follow-up (mos.)	Diagnosis	Side	Type of Excision	Patella	Length of Resection (cm)	Quadriceps Heads Excised	Functional Score
Group 1
1	M, 25	44	Osteogenic sarcoma	R	Extra-articular	Partially removed	14	Vastus medialis and vastus intermedius	Good
2	M, 23	38	Malignant fibrohistio-cytoma	L	Intra-articular	Not removed	16	Vastus medialis	Good
3	M, 29	37	Osteogenic sarcoma	L	Intra-articular	Not removed	16	Vastus medialis and vastus intermedius	Good
4	M, 26	44	Osteogenic sarcoma	R	Intra-articular	Not removed	16	Vastus medialis	Excellent
5	M, 18	23	Osteogenic sarcoma	R	Intra-articular	Not removed	20	Vastus medialis and vastus intermedius	Excellent
6	M, 22	55	Osteogenic sarcoma	L	Intra-articular	Not removed	20	Vastus medialis and vastus intermedius	Excellent
7	F, 30	22	Osteogenic sarcoma	L	Intra-articular	Not removed	12	Vastus medialis and vastus intermedius	Good
Group 2
8	M, 51	48	Fibro- sarcoma	L	Extra-articular	Partially removed	16	Vastus lateralis and vastus intermedius	Good
9	F, 27	36	Osteogenic sarcoma	R	Extra-articular	Partially removed	18	Vastus lateralis and vastus intermedius	Good
10	F, 40	68	Osteogenic sarcoma	L	Intra-articular	Not removed	14	Vastus lateralis and vastus intermedius	Good
11	M, 40	33	Malignant fibrohistio-cytoma	R	Intra-articular	Not removed	18	Vastus lateralis and vastus intermedius	Good
12	M, 24	104	Osteogenic sarcoma	R	Intra-articular	Not removed	18	Vastus lateralis and vastus intermedius	Excellent
13	M, 50	34	Osteogenic sarcoma	R	Intra-articular	Not removed	14	Vastus lateralis and vastus intermedius	Good
14	M, 20	53	Osteogenic sarcoma	R	Intra-articular	Not removed	18	Vastus lateralis and vastus intermedius	Excellent
15	F, 19	35	Osteogenic sarcoma	R	Intra-articular	Not removed	16	Vastus lateralis and vastus intermedius	Excellent
16	M, 20	22	Osteogenic sarcoma	L	Intra-articular	Not removed	20	Vastus lateralis and vastus intermedius	Excellent

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TABLE II: Difference Between the Treated and the Contralateral Knee with Respect to Extensor Peak Torque on Isometric Muscle-Strength Testing

*The values are given as the mean and the standard deviation.†According to analysis of variance. NS = not significant.‡According to the Mann-Whitney U test.

Knee Angle (degrees)	Group 1* (Medial) (percent)	Group 2* (Lateral) (percent)	P Value†
90	-79.7 ± 9.9	-75.8 ± 11.4	NS
60	-74.3 ± 9.2	-65.4 ± 13.7	NS
30	-58.6 ± 17.4	-43.6 ± 22.2	NS
0	-33.6 ± 32.4	-39.8 ± 20.2	NS‡

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TABLE II: Difference Between the Treated and the Contralateral Knee with Respect to Extensor Peak Torque on Isometric Muscle-Strength Testing

*The values are given as the mean and the standard deviation.†According to analysis of variance. NS = not significant.‡According to the Mann-Whitney U test.

Knee Angle (degrees)	Group 1* (Medial) (percent)	Group 2* (Lateral) (percent)	P Value†
90	-79.7 ± 9.9	-75.8 ± 11.4	NS
60	-74.3 ± 9.2	-65.4 ± 13.7	NS
30	-58.6 ± 17.4	-43.6 ± 22.2	NS
0	-33.6 ± 32.4	-39.8 ± 20.2	NS‡

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TABLE III: Gait-Analysis Data

	P Value*	Control Group†	Group 1† (Medial)	Group 2† (Lateral)	P Value According to Scheffé F Test
Control Group Compared with Group 1	Control Group Compared with Group 2	Group 1 Compared with Group 2
Time-distance parameters
Stance phase (percent of stride)	NS	60.4 ± 2.0	59.8 ± 1.4	60.9 ± 1.8	NS	NS	NS
Stride length (percent of height)	0.01‡	83.3 ± 7.5	79.9 ± 5.5	80 ± 9.9	0.05	NS	NS
Cycle time (secs.)	0.001‡	1.12 ± 0.09	1.19 ± 0.08	1.17 ± 0.1	0.01	0.03	NS
Cadence (stride/min.)	0.001	53.9 ± 4.2	50.6 ± 3.4	51.15 ± 4.2	0.006	0.03	NS
Speed of progression (cm/sec.)	0.002	125.6 ± 16.8	115.4 ± 13.6	115.2 ± 17.1	0.035	0.015	NS
Ground-reaction forces (percent of body weight)
F1	<0.0001	112 ± 8.9	100.4 ± 7.4	97.3 ± 4.4	<0.0001	<0.0001	NS
F2	<0.0001	73 ± 6.8	80.6 ± 4.4	81.1 ± 5.9	<0.0001	<0.0001	NS
F3	<0.0001	114 ± 6.5	101.3 ± 5.9	106 ± 5.9	<0.0001	<0.0001	NS
F4	0.018‡	4.5 ± 3.4	2.5 ± 2	2.9 ± 2.4	0.003	NS	NS
F5	<0.0001‡	-19.3 ± 4.2	-16.8 ± 4.8	-14.8 ± 2.5	<0.0001	<0.0001	NS
F6	<0.0001	21.7 ± 4.3	18.4 ± 2.8	17.4 ± 3.3	<0.0001	<0.0001	NS
F7	<0.0001	-4.7 ± 2.0	-2.1 ± 2.3	-2.7 ± 1.7	<0.0001	<0.0001	NS
F8	NS‡	6.6 ± 1.3	6 ± 1.4	6 ± 1.4	NS	NS	NS
F9	0.003‡	5.5 ± 1.9	7 ± 1.7	5.7 ± 1.2	0.004	NS	0.02
Knee-angle parameters (degrees)
K1	NS	0.4 ± 4.8	0.5 ± 3.8	2.3 ± 5.3	NS	NS	NS
K2	<0.0001	17.9 ± 7.6	5.7 ± 5.7	11.1 ± 7.9	<0.0001	<0.0001	0.049
K3	NS	4.9 ± 4.5	3.9 ± 4.6	6.8 ± 6.7	NS	NS	NS
K4	0.002	36.6 ± 7.6	42.6 ± 7.1	39.6 ± 7.5	0.004	NS	NS
K5	NS	65.6 ± 5.2	65.4 ± 5.1	65.6 ± 8.7	NS	NS	NS
K6	NS	60.7 ± 5.1	61.4 ± 8.7	58.7 ± 11.8	NS	NS	NS
External knee moment parametersÂ§
KM1	<0.0001‡	-4.2 ± 1.3	-3.1 ± 0.8	-3.4 ± 0.9	<0.0001	0.02	NS
KM2	<0.0001‡	1.4 ± 2.0	-0.6 ± 0.9	-0.5 ± 1.5	<0.0001	<0.0001	NS
KM3	0.0001‡	-2.7 ± 1.4	-1.7 ± 0.9	-1.9 ± 1.9	<0.0001	NS	<0.0001
KM4	0.001	1 ± 0.6	0.8 ± 0.5	0.5 ± 0.5	NS	0.001	NS
KM5	<0.0001	-2.3 ± 1.1	-1.1 ± 0.5	-1.9 ± 0.7	<0.0001	NS	NS
KM6	0.001‡	-1.6 ± 1.0	-0.9 ± 0.6	-1.9 ± 0.5	<0.0001	NS	<0.0001
KM7	NS‡	-0.24 ± 0.41	-0.3 ± 0.18	-0.11 ± 0.14	NS	NS	NS
KM8	0.0004	1 ± 0.45	0.7 ± 0.25	0.9 ± 0.42	0.021	NS	NS

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TABLE III: Gait-Analysis Data

	P Value*	Control Group†	Group 1† (Medial)	Group 2† (Lateral)	P Value According to Scheffé F Test
Control Group Compared with Group 1	Control Group Compared with Group 2	Group 1 Compared with Group 2
Time-distance parameters
Stance phase (percent of stride)	NS	60.4 ± 2.0	59.8 ± 1.4	60.9 ± 1.8	NS	NS	NS
Stride length (percent of height)	0.01‡	83.3 ± 7.5	79.9 ± 5.5	80 ± 9.9	0.05	NS	NS
Cycle time (secs.)	0.001‡	1.12 ± 0.09	1.19 ± 0.08	1.17 ± 0.1	0.01	0.03	NS
Cadence (stride/min.)	0.001	53.9 ± 4.2	50.6 ± 3.4	51.15 ± 4.2	0.006	0.03	NS
Speed of progression (cm/sec.)	0.002	125.6 ± 16.8	115.4 ± 13.6	115.2 ± 17.1	0.035	0.015	NS
Ground-reaction forces (percent of body weight)
F1	<0.0001	112 ± 8.9	100.4 ± 7.4	97.3 ± 4.4	<0.0001	<0.0001	NS
F2	<0.0001	73 ± 6.8	80.6 ± 4.4	81.1 ± 5.9	<0.0001	<0.0001	NS
F3	<0.0001	114 ± 6.5	101.3 ± 5.9	106 ± 5.9	<0.0001	<0.0001	NS
F4	0.018‡	4.5 ± 3.4	2.5 ± 2	2.9 ± 2.4	0.003	NS	NS
F5	<0.0001‡	-19.3 ± 4.2	-16.8 ± 4.8	-14.8 ± 2.5	<0.0001	<0.0001	NS
F6	<0.0001	21.7 ± 4.3	18.4 ± 2.8	17.4 ± 3.3	<0.0001	<0.0001	NS
F7	<0.0001	-4.7 ± 2.0	-2.1 ± 2.3	-2.7 ± 1.7	<0.0001	<0.0001	NS
F8	NS‡	6.6 ± 1.3	6 ± 1.4	6 ± 1.4	NS	NS	NS
F9	0.003‡	5.5 ± 1.9	7 ± 1.7	5.7 ± 1.2	0.004	NS	0.02
Knee-angle parameters (degrees)
K1	NS	0.4 ± 4.8	0.5 ± 3.8	2.3 ± 5.3	NS	NS	NS
K2	<0.0001	17.9 ± 7.6	5.7 ± 5.7	11.1 ± 7.9	<0.0001	<0.0001	0.049
K3	NS	4.9 ± 4.5	3.9 ± 4.6	6.8 ± 6.7	NS	NS	NS
K4	0.002	36.6 ± 7.6	42.6 ± 7.1	39.6 ± 7.5	0.004	NS	NS
K5	NS	65.6 ± 5.2	65.4 ± 5.1	65.6 ± 8.7	NS	NS	NS
K6	NS	60.7 ± 5.1	61.4 ± 8.7	58.7 ± 11.8	NS	NS	NS
External knee moment parametersÂ§
KM1	<0.0001‡	-4.2 ± 1.3	-3.1 ± 0.8	-3.4 ± 0.9	<0.0001	0.02	NS
KM2	<0.0001‡	1.4 ± 2.0	-0.6 ± 0.9	-0.5 ± 1.5	<0.0001	<0.0001	NS
KM3	0.0001‡	-2.7 ± 1.4	-1.7 ± 0.9	-1.9 ± 1.9	<0.0001	NS	<0.0001
KM4	0.001	1 ± 0.6	0.8 ± 0.5	0.5 ± 0.5	NS	0.001	NS
KM5	<0.0001	-2.3 ± 1.1	-1.1 ± 0.5	-1.9 ± 0.7	<0.0001	NS	NS
KM6	0.001‡	-1.6 ± 1.0	-0.9 ± 0.6	-1.9 ± 0.5	<0.0001	NS	<0.0001
KM7	NS‡	-0.24 ± 0.41	-0.3 ± 0.18	-0.11 ± 0.14	NS	NS	NS
KM8	0.0004	1 ± 0.45	0.7 ± 0.25	0.9 ± 0.42	0.021	NS	NS

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TABLE IV: Present or Prolonged Activity of the Rectus Femoris During Stance Phase*

*The difference between Group 1 and Group 2 was found to be significant (Fisher exact test, p = 0.018).

	Group 1 (Medial)	Group 2 (Lateral)	Total
No. (percent) of gait trials with activity	9 (43)	21 (78)	30 (63)
No. (percent) of gait trials with reduced or absent activity	12 (57)	6 (22)	18 (38)
Total no. (percent) of gait trials	21 (100)	27 (100)	48 (100)

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TABLE IV: Present or Prolonged Activity of the Rectus Femoris During Stance Phase*

*The difference between Group 1 and Group 2 was found to be significant (Fisher exact test, p = 0.018).

	Group 1 (Medial)	Group 2 (Lateral)	Total
No. (percent) of gait trials with activity	9 (43)	21 (78)	30 (63)
No. (percent) of gait trials with reduced or absent activity	12 (57)	6 (22)	18 (38)
Total no. (percent) of gait trials	21 (100)	27 (100)	48 (100)