JBJS | Bone-Grafting for Severe Patellar Bone Loss During Revision Knee Arthroplasty

The Journal of Bone & Joint Surgery, Volume 83, Issue 2

Articles | February 01, 2001

Bone-Grafting for Severe Patellar Bone Loss During Revision Knee Arthroplasty

Arlen D. Hanssen, MD

Investigation performed at the Department of Orthopedic Surgery, Mayo Clinic and Mayo Foundation, Rochester, Minnesota
Arlen D. Hanssen, MD Department of Orthopedic Surgery, Mayo Clinic and Mayo Foundation, 200 First Street S.W., Rochester, MN 55905
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.

The Journal of Bone & Joint Surgery. 2001; 83:171-171

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Abstract

Background: Severe patellar bone loss may preclude adequate fixation of another patellar prosthesis as a part of revision knee replacement. The purpose of this study was to describe the surgical technique and early clinical results of an alternative to the conventional treatment options of either patellectomy or retention of the remaining patellar osseous shell. The goals of this procedure are to restore patellar bone stock and potentially to improve the functional outcome.

Methods: Severe patellar bone loss had left a "patellar shell" that precluded insertion of another patellar implant in nine of 100 consecutive knees undergoing revision total knee arthroplasty. Rather than performing a patellectomy or simply retaining the patellar osseous shell in these nine knees (eight patients), I performed a surgical procedure in which a tissue flap was secured to the patellar rim to contain cancellous bone graft inserted into the patellar bone defect. Final follow-up was at a mean of 36.7 months (range, twenty-four to fifty-five months) after the patellar bone-grafting procedure.

Results: The mean preoperative Knee Society scores for function and pain were 39 points (range, 18 to 82 points) and 40 points (range, 20 to 80 points), respectively. At the time of final follow-up, the Knee Society function and pain scores had improved significantly, to a mean function score of 91 points (range, 80 to 98 points) and a mean pain score of 84 points (range, 65 to 100 points) (p < 0.05). The point of greatest patellar thickness measured intraoperatively ranged from 7 to 9 mm. Patellar thickness on immediate postoperative Merchant radiographs averaged 22 mm (range, 20 to 25 mm) whereas, at the time of final follow-up, patellar thickness averaged 19.7 mm (range, 17 to 22.5 mm).

Conclusions: In contrast with other treatment alternatives, this surgical procedure imparts the potential for restoring patellar bone stock and may improve functional outcome by facilitating patellar tracking and improving quadriceps leverage. On the basis of satisfactory short-term to mid-term clinical results, this technique of patellar bone-grafting appears to be an important addition to the armamentarium of surgeons performing revision knee arthroplasties.

Figures in this Article

Introduction

Introduction | Materials and Methods | Results | Discussion | References

At the time of revision knee arthroplasty, there may be substantial loss of patellar bone stock secondary to bone resection during prior arthroplasties, osteolysis resulting from wear debris, or removal of a well-fixed patellar prosthesis. When possible, it is preferable to insert another patellar implant as a part of the revision knee replacement^1,2, but occasionally the magnitude of patellar bone loss precludes adequate fixation of another patellar prosthesis. The traditional treatment options in this setting have been either patellectomy or retention of the remaining patellar osseous shell^3,4.

Although primary or revision total knee arthroplasty in patients with a prior patellectomy is an acceptable procedure, its functional outcomes have been inferior to those of total knee arthroplasty performed in patients with a patella^5-8. Patellectomies performed as a part of a revision knee replacement have been associated with markedly inferior functional results as well as difficulties with weakness or delayed disruption of the extensor mechanism^5,9. As a consequence, most authors have not performed a patellectomy in conjunction with a revision knee replacement and have attempted to retain the patellar osseous shell. Retention of the osseous shell (patellar resection arthroplasty) has also been associated with inferior clinical results, as reflected by lower knee scores, persistent retropatellar pain, patellar maltracking, difficulty with stair-climbing, and delayed patellar fragmentation^3,4.

The purpose of the present study was to report the early clinical results of a novel surgical technique designed to restore patellar bone stock and potentially to improve function in patients with severe patellar bone deficiency during revision total knee arthroplasty. To my knowledge this technique has not been previously described.

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Fig. 1:: A The "patellar shell." Severe loss of patellar bone stock has left only the anterior cortex, variable amounts of the patellar rim, and an irregular cavitary surface to the remaining patellar bone. B Peripheral suture fixation of the tissue flap into the patellar rim and surrounding peripatellar fibrous tissue. C Insertion of the cancellous bone graft into the purse-string opening of the tissue flap-patellar shell construct. D After final impaction of bone graft into the patellar defect, the opening of the tissue flap is closed with additional sutures to provide a watertight closure to contain the bone graft.

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Fig. 2:: Fig. 2, A, B, and C Case 2. A Merchant radiograph of a laterally malpositioned patellar component with maltracking and polyethylene wear. Removal of the patellar component was associated with severe patellar bone loss, which precluded fixation of another patellar component. B Merchant radiograph made three months after patellar bone-grafting. The arrows indicate the junction of the bone graft and the patellar shell. C Merchant radiograph made forty-nine months after patellar bone-grafting, revealing incorporation of the patellar bone graft with evidence of trabecular formation.

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Fig. 3:: Case 1. Merchant radiograph made fifty-five months after patellar bone-grafting, revealing compression bone-grafting with remolding over the lateral femoral condyle. The bone graft has remolded with a central projection into the femoral trochlea.

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TABLE I: Data on Nine Knees Treated with Patellar Bone-Grafting

*PTA = posttraumatic arthritis, and OA = osteoarthritis.

Case	Side	Gender, Age (yr)	Reason for Revision	Diagnosis*	Preop. Knee Society Score^11 (points)		Preop. Range of Motion (deg)			Source of Graft	Flap Type	Postop. Knee Society Score¹¹ (points)		Postop. Range of Motion (deg)			Durat. of Follow-up (mo)
Function	Pain	Ext.	Flex.	Flex.-Ext. Arc	Function	Pain	Ext.	Flex.	Flex.-Ext. Arc
1	L	M, 65	Flex. contract., stiffness, patellar osteolysis	PTA	50	23	25	90	65	Autograft	Peripatellar fibrotic tissue	80	65	5	115	110	55
2	L	F, 60	Knee instabil., patellar malposition with maltracking and polyethylene wear	OA	35	36	0	105	105	Autograft	Peripatellar fibrotic tissue	93	90	0	115	115	49
3	R	F, 64	Polyethylene wear, osteolysis	OA	18	40	15	40	25	Allograft	Fascia lata	93	90	0	90	90	42
	L	F, 64	Polyethylene wear, osteolysis	OA	26	40	10	90	80	Allograft	Fascia lata	93	90	0	90	90	37
4	L	F, 76	Polyethylene wear, osteolysis	OA	45	31	0	90	90	Autograft	Peripatellar fibrotic tissue	98	100	0	115	115	31
5	R	M, 74	Polyethylene wear, osteolysis	OA	47	40	0	60	60	Allograft	Fascia lata	89	80	0	95	95	30
6	L	M, 45	Polyethylene wear, osteolysis	PTA	24	50	0	90	90	Allograft	Suprapatellar free tissue	88	80	0	90	90	36
7	L	M, 75	Polyethylene wear, osteolysis	OA	82	80	5	90	85	Allograft	Suprapatellar free tissue	93	90	0	90	90	26
8	L	M, 68	Aseptic loosening of femur, tibia, patella	OA	25	20	5	90	85	Autograft	Peripatellar fibrotic tissue	92	70	5	90	85	24

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TABLE I: Data on Nine Knees Treated with Patellar Bone-Grafting

*PTA = posttraumatic arthritis, and OA = osteoarthritis.

Case	Side	Gender, Age (yr)	Reason for Revision	Diagnosis*	Preop. Knee Society Score^11 (points)		Preop. Range of Motion (deg)			Source of Graft	Flap Type	Postop. Knee Society Score¹¹ (points)		Postop. Range of Motion (deg)			Durat. of Follow-up (mo)
Function	Pain	Ext.	Flex.	Flex.-Ext. Arc	Function	Pain	Ext.	Flex.	Flex.-Ext. Arc
1	L	M, 65	Flex. contract., stiffness, patellar osteolysis	PTA	50	23	25	90	65	Autograft	Peripatellar fibrotic tissue	80	65	5	115	110	55
2	L	F, 60	Knee instabil., patellar malposition with maltracking and polyethylene wear	OA	35	36	0	105	105	Autograft	Peripatellar fibrotic tissue	93	90	0	115	115	49
3	R	F, 64	Polyethylene wear, osteolysis	OA	18	40	15	40	25	Allograft	Fascia lata	93	90	0	90	90	42
	L	F, 64	Polyethylene wear, osteolysis	OA	26	40	10	90	80	Allograft	Fascia lata	93	90	0	90	90	37
4	L	F, 76	Polyethylene wear, osteolysis	OA	45	31	0	90	90	Autograft	Peripatellar fibrotic tissue	98	100	0	115	115	31
5	R	M, 74	Polyethylene wear, osteolysis	OA	47	40	0	60	60	Allograft	Fascia lata	89	80	0	95	95	30
6	L	M, 45	Polyethylene wear, osteolysis	PTA	24	50	0	90	90	Allograft	Suprapatellar free tissue	88	80	0	90	90	36
7	L	M, 75	Polyethylene wear, osteolysis	OA	82	80	5	90	85	Allograft	Suprapatellar free tissue	93	90	0	90	90	26
8	L	M, 68	Aseptic loosening of femur, tibia, patella	OA	25	20	5	90	85	Autograft	Peripatellar fibrotic tissue	92	70	5	90	85	24

Materials and Methods

Introduction | Materials and Methods | Results | Discussion | References

Between November 1995 and May 1998, I performed 100 consecutive revision knee arthroplasties. The procedure included a patellar bone-grafting procedure in nine knees (eight patients) after it had been determined that the magnitude of patellar bone loss precluded fixation of another patellar implant. The patellar bone loss in these patients was categorized as severe cavitary patellar bone loss with only the anterior cortex and variable amounts of the peripheral patellar rim remaining (Fig. 1Fig. 1, A). The patellar bone-grafting procedure was performed as an alternative to either patellar resection arthroplasty or patellectomy.

There were three women and five men, with a mean age of 65.9 years (range, forty-five to seventy-six years) at the time of the revision knee arthroplasty and patellar bone-grafting (Table ITable I). Seven procedures were on the left knee, and two were on the right. The reason for the initial knee arthroplasty was osteoarthritis in seven knees (six patients) and posttraumatic arthritis in the other two. The reason for the revision knee surgery was polyethylene wear with severe osteolysis in six knees, tibiofemoral instability with patellar maltracking and polyethylene wear in one (Fig. 2Fig. 2, A), aseptic loosening of all arthroplasty components in one, and flexion contracture with stiffness and patellar osteolysis in one. The patellae in this study were revised because of loosening of the patellar component (four knees), polyethylene wear in the presence of a metal-backed patella (four knees), or malposition of the patellar component (one knee). Seven knees (six patients) had had only one prior knee arthroplasty, one had had two, and one had had three.

All patients had a knee aspiration as part of the preoperative evaluation to rule out the presence of deep periprosthetic infection. Intraoperative tissue specimens from the nine knees were sent for culture and sensitivity testing, and there was no growth. The tibial and femoral implants that were removed included those of an uncemented cruciate-sacrificing LCS rotating-platform prosthesis (DePuy, Warsaw, Indiana) in one knee, those of an uncemented cruciate-retaining Maxim prosthesis in three knees (Biomet, Warsaw, Indiana), those of a cemented posterior stabilized Genesis prosthesis (Smith-Nephew Richards, Memphis, Tennessee) in one knee, those of a cemented cruciate-retaining PFC prosthesis (Johnson and Johnson, Raynham, Massachusetts) in one knee, those of an Insall-Burstein-II prosthesis (Zimmer, Warsaw, Indiana) in two knees, and those of an uncemented PCA cruciate-retaining prosthesis (Howmedica, Rutherford, New Jersey) in one knee. Of the nine patellar implants that were removed, five were of an uncemented metal-backed design and four were cemented all-polyethylene components.

All patients had concomitant revision of the femoral and tibial components at the time of the patellar bone-grafting. In addition to the severe patellar bone loss, associated femoral bone deficiencies included one F2-A defect and eight F2-B defects, as classified according to the system of Engh and Ammeen¹⁰. There were also two T2-A and seven T2-B tibial bone defects, as classified with the same system. All of the femoral and tibial components inserted at the revision arthroplasty were of the same posterior stabilized knee design (PFC Sigma; Johnson and Johnson), and all were fixed with acrylic bone cement. All but one of the components were stemmed.

Knee scores were calculated with use of the Knee Society knee-scoring system¹¹. With this system, the patient is assigned a score for pain and a score for function, each with a maximum of 100 points. Radiographs at each examination included anteroposterior standing radiographs, Merchant patellar radiographs, and lateral radiographs made with fluoroscopic positioning and use of magnification markers to allow accurate measurements of patellar height. Surveillance was continued for a minimum of two years. Institutional approval and the consent of all patients were obtained prior to this review, and no patient refused to participate in the study. All patients returned for clinical and radiographic examination at three months and one year postoperatively and annually thereafter. Final follow-up was at a mean of 36.7 months (range, twenty-four to fifty-five months) after the patellar bone-grafting procedure. No patient was lost to follow-up.

Statistical Analysis

The data in this study were evaluated with analysis of variance. Significance was set at p < 0.05.

Surgical Technique

If, at the time of revision surgery, it is determined that the magnitude of patellar bone loss precludes fixation of another patellar implant, it is helpful to retain the pseudomeniscus of scar tissue and most of the peripatellar fibrotic tissue to facilitate suture fixation of the tissue flap to the patellar rim. The patellar shell is prepared by removing all fibrous membrane in the crevices of the remaining patellar bone (Fig. 1Fig. 1, A). The tissue flap is created from one of several sources, including large flaps of peripatellar fibrotic tissue or a free tissue flap obtained from either the suprapatellar pouch or the fascia lata in the lateral gutter of the knee joint. The tissue flap is sewn to the peripheral patellar rim and peripatellar fibrotic tissue with multiple, nonabsorbable size-0 sutures to provide a watertight closure (Fig. 1Fig. 1, B). A small purse-string opening is left in one portion of the tissue flap repair to facilitate delivery of bone graft into the patellar defect (Fig. 1Fig. 1, C).

Cancellous autograft is harvested from the metaphyseal portion of the central part of the femur during preparation of the femur for the revision implant. In the absence of locally available cancellous autograft, cancellous allograft bone has been used. The bone graft is prepared by morseling the bone into small fragments of approximately 5 to 8 mm in height and width, as this size facilitates tight impaction of the bone graft into the patellar shell-tissue flap construct. The bone graft is tightly impacted through the opening of the fascial flap into the patellar bone defect, with enough volume so that the final patellar construct has a height of more than 20 mm. The tissue flap is then closed completely to contain the bone graft within the patellar shell (Fig. 1Fig. 1, D). The adequacy of the suture repair is examined to ensure that the tissue flap securely contains the impacted bone graft. The peripatellar arthrotomy site is provisionally repaired with several sutures or towel clips to mold the patellar construct in the femoral trochlea as the knee is placed through the full range of motion. Postoperative rehabilitation is the same as the usual protocol following revision knee arthroplasty.

Results

Introduction | Materials and Methods | Results | Discussion | References

Intraoperative measurement of the remaining patellar bone stock was attempted in all nine knees (eight patients); however, it became obvious that linear measurements of patellar height are extremely difficult. These "patellar shells" are irregular in contour, and in many areas of the patella only several millimeters of cortical bone remained. The point of greatest thickness of the patella measured 9 mm in two knees, 8 mm in three, and 7 mm in four. The tissue flap used to secure the bone graft in the patellar construct consisted of peripatellar fibrotic tissue only in four knees, fascia lata from the iliotibial tract in three knees, and tissue harvested from the suprapatellar pouch in two knees. As for the bone graft, an autograft from the distal part of the femur was used in four knees and allograft femoral head was used in five knees.

Preoperatively, the range of extension of the knee averaged 6.7° (range, 0° to 25°) and the range of flexion averaged 82.8° (range, 40° to 105°), for an average motion arc of 76.1° (range, 25° to 105°). The mean preoperative Knee Society scores for function and pain were 39 points (range, 18 to 82 points) and 40 points (range, 20 to 80 points), respectively. At the time of final follow-up, extension averaged 1.1° (range, 0° to 5°), flexion averaged 98.9° (range, 90° to 115°), and the knee motion arc averaged 97.8° (range, 85° to 115°) (p < 0.05). The Knee Society scores for function and pain had improved significantly, to a mean of 91 points (range, 80 to 98 points) and 84 points (range, 65 to 100 points) (p < 0.05), respectively.

Radiographic analysis at the time of final follow-up revealed that the patella was centrally located within the prosthetic femoral trochlea in five knees (Fig. 2Fig. 2, C). The patellar construct had remolded over the lateral femoral condyle in four knees (Fig. 3Fig. 3). The patellae with lateral remolding all had a deeper central protrusion of patellar bone within the trochlea of the prosthetic femur. Patellar height on the immediate postoperative Merchant radiographs averaged 22 mm (range, 20 to 25 mm), whereas patellar height on Merchant radiographs made at the time of final follow-up averaged 19.7 mm (range, 17 to 22.5 mm).

Reoperation and Complications

In one patient (Case 2), arthrofibrosis developed three weeks postoperatively, and the patient required manipulation under anesthesia to increase the range of motion of the knee. Eighteen months later she underwent a reoperation to exchange the tibial polyethylene liner for a thicker one in order to treat progressive tibiofemoral instability. At surgery the patellar tissue flap was intact and had the gross appearance of smooth fibrocartilage. A small core biopsy of patellar bone obtained from the region of the medial patellar facet revealed empty lacunae and fragments of dead bone spicules without evidence of revascularization.

In another patient (Case 1), anterior knee pain developed fifty-five months postoperatively. The diagnosis of femoral loosening was made on the basis of a comparison of serial radiographs, which revealed migration of the femoral component into a position of flexion. This component was the only unstemmed femoral component used in this group of patients. It is unclear at this time whether the anterior knee pain was due to the loosening of the femoral component or to the lateral patellar remolding and corresponding sclerosis of the lateral patellar facet (Fig. 3Fig. 3). At the time of this writing, the patient was awaiting surgery for revision of the loose femoral component. Because patellar bone stock had been restored, insertion of another patellar component as a part of the upcoming revision surgery, if the patellar bone stock was of acceptable quality, was discussed with the patient.

Discussion

Introduction | Materials and Methods | Results | Discussion | References

The concept of patellar bone-grafting was initially described for total knee arthroplasties in patients who had had a prior patellectomy¹². A 2.5-cm-wide and 1-cm-thick structural bone graft was secured in a subsynovial pouch of the patellar tendon in the location of the anatomic position of the previous patella. The purpose of this procedure was to increase the moment arm of the extensor mechanism and to improve the stabilizing characteristics of the knee joint in the sagittal plane. On the basis of the results in six patients (seven knees), it was concluded that patellar bone-grafting improved quadriceps leverage and was useful in restoring extensor mechanism function¹².

The concept of tissue being sewn into the peripheral patellar rim to contain bone graft within the patellar shell evolved from the description by Cave and Rowe¹³. They described a surgical procedure in which the degenerated surface of the patella is covered with a portion of the infrapatellar fat pad, which is elevated and sewn peripherally into the patellar rim to be interposed between the patella and the femoral trochlea.

The procedure of patellar bone-grafting that I described relies on the presence of an osseous patellar shell, impaction of cancellous bone graft into the defect, and containment of the bone graft with soft tissue secured into the peripheral patellar rim. Postoperatively the retropatellar surface of the construct undergoes continued remodeling against the prosthetic femoral trochlea, with the tissue flap serving as an interpositional tissue arthroplasty. This retropatellar remodeling allows the patellar construct to assume the shape of the prosthetic trochlear groove during the range of motion of the knee and other retropatellar compressive forces that occur with functional activities of the knee joint.

The design and shape of the femoral trochlea may be another important factor, although it is not possible to draw conclusions about this from the data in the current study. It seems intuitive that an anatomically normal patellar groove would facilitate proper molding of the patellar bone graft. It is also important to note that all nine procedures described in this report included concomitant femoral and tibial revision arthroplasty with careful attention directed toward achieving proper rotational alignment of the femoral and tibial components. It may be that, with isolated patellar bone-grafting, the graft would be vulnerable to femoral or tibial malrotation, which would predispose toward lateral patellar subluxation and abnormal remodeling of the patellar bone graft. It seems reasonable to state that, if patellar bone-grafting is to be performed as an isolated procedure, the rotational position of the existing femoral and tibial components should be assessed carefully.

The current study is limited by the lack of a comparison group of patients who had a similar patellar bone deficiency during revision knee arthroplasty and were treated with either retention of the patellar shell or patellectomy. In a study comparing patellar replacement with retention of the osseous shell, the latter procedure yielded lower-quality results³, although it should be noted that the patients in whom the patella was not suitable for another patellar implant may have had other factors that predisposed toward a lower-quality result. In view of the findings of that study, it appears that the results obtained with patellar bone-grafting in the current study are more comparable with the results obtained with implantation of another patellar implant rather than with those obtained with retention of a patellar osseous shell.

Severe patellar bone deficiency that precludes fixation of another patellar implant has remained a rare yet important problem during revision knee arthroplasty. In contrast with the treatment alternative of patellectomy or retention of the osseous shell, the new surgical procedure described in the present report imparts the potential for restoration of patellar bone stock and may improve functional outcome by facilitating patellar tracking and improving quadriceps leverage. The procedure is simple to perform and does not require sophisticated instrumentation or a long learning curve. On the basis of the current satisfactory short-term to mid-term clinical results, I believe that this surgical procedure is an important addition to the armamentarium of surgeons performing revision knee arthroplasty.

References

Introduction | Materials and Methods | Results | Discussion | References

Bayley JC; Scott RD; Ewald FC; and Holmes GB Jr: Failure of the metal-backed patellar component after total knee replacement. J Bone Joint Surg Am,1988.70: 668-74, 70668 1988 [PubMed]

Berry DJ, and Rand JA: Isolated patellar component revision of total knee arthroplasty. Clin Orthop,1993.286: 110-5, 286110 1993 [PubMed]

Barrack RL; Matzkin E; Ingraham R; Engh G; and Rorabeck C: Revision knee arthroplasty with patella replacement versus bony shell. Clin Orthop,1998.356: 139-43, 356139 1998 [PubMed]

Pagnano MW; Scuderi GR; and Insall JN: Patellar component resection in revision and reimplantation total knee arthroplasty. Clin Orthop,1998.356: 134-8, 356134 1998 [PubMed]

Dennis DA: Extensor mechanism problems in total knee arthroplasty. Instr Course Lect,1997.46: 171-80, 46171 1997 [PubMed]

Kang JD; Papas SN; Rubash HE; and McClain EJ Jr: Total knee arthroplasty in patellectomized patients. J Arthroplasty,1993.8: 489-501, 8489 1993 [PubMed]

Martin SD; Haas SB; and Insall JN: Primary total knee arthroplasty after patellectomy. J Bone Joint Surg Am,1995.77: 1323-30, 771323 1995 [PubMed]

Paletta GA Jr, and Laskin RS: Total knee arthroplasty after a previous patellectomy. J Bone Joint Surg Am,1995.77: 1708-12, 771708 1995 [PubMed]

Laskin RS: Management of the patella during revision total knee replacement arthroplasty. Orthop Clin North Am,1998.29: 355-60, 29355 1998 [PubMed]

Engh GA, and Ammeen DJ: Bone loss with revision total knee arthroplasty: defect classification and alternatives for reconstruction. Instr Course Lect,1999.48: 167-75, 48167 1999 [PubMed]

Insall JN; Dorr LD; Scott RD; and Scott WN: Rationale of the Knee Society clinical rating system. Clin Orthop,1989.248: 13-4, 24813 1989 [PubMed]

Buechel FF: Patellar tendon bone grafting for patellectomized patients having total knee arthroplasty. Clin Orthop,1991.271: 72-8, 27172 1991 [PubMed]

Cave EF, and Rowe CR: The patella. Its importance in derangement of the knee. J Bone Joint Surg Am,1950.32: 542-53, 32542 1950 [PubMed]

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TABLE I: Data on Nine Knees Treated with Patellar Bone-Grafting

*PTA = posttraumatic arthritis, and OA = osteoarthritis.

Case	Side	Gender, Age (yr)	Reason for Revision	Diagnosis*	Preop. Knee Society Score^11 (points)		Preop. Range of Motion (deg)			Source of Graft	Flap Type	Postop. Knee Society Score¹¹ (points)		Postop. Range of Motion (deg)			Durat. of Follow-up (mo)
Function	Pain	Ext.	Flex.	Flex.-Ext. Arc	Function	Pain	Ext.	Flex.	Flex.-Ext. Arc
1	L	M, 65	Flex. contract., stiffness, patellar osteolysis	PTA	50	23	25	90	65	Autograft	Peripatellar fibrotic tissue	80	65	5	115	110	55
2	L	F, 60	Knee instabil., patellar malposition with maltracking and polyethylene wear	OA	35	36	0	105	105	Autograft	Peripatellar fibrotic tissue	93	90	0	115	115	49
3	R	F, 64	Polyethylene wear, osteolysis	OA	18	40	15	40	25	Allograft	Fascia lata	93	90	0	90	90	42
	L	F, 64	Polyethylene wear, osteolysis	OA	26	40	10	90	80	Allograft	Fascia lata	93	90	0	90	90	37
4	L	F, 76	Polyethylene wear, osteolysis	OA	45	31	0	90	90	Autograft	Peripatellar fibrotic tissue	98	100	0	115	115	31
5	R	M, 74	Polyethylene wear, osteolysis	OA	47	40	0	60	60	Allograft	Fascia lata	89	80	0	95	95	30
6	L	M, 45	Polyethylene wear, osteolysis	PTA	24	50	0	90	90	Allograft	Suprapatellar free tissue	88	80	0	90	90	36
7	L	M, 75	Polyethylene wear, osteolysis	OA	82	80	5	90	85	Allograft	Suprapatellar free tissue	93	90	0	90	90	26
8	L	M, 68	Aseptic loosening of femur, tibia, patella	OA	25	20	5	90	85	Autograft	Peripatellar fibrotic tissue	92	70	5	90	85	24

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TABLE I: Data on Nine Knees Treated with Patellar Bone-Grafting

*PTA = posttraumatic arthritis, and OA = osteoarthritis.

Case	Side	Gender, Age (yr)	Reason for Revision	Diagnosis*	Preop. Knee Society Score^11 (points)		Preop. Range of Motion (deg)			Source of Graft	Flap Type	Postop. Knee Society Score¹¹ (points)		Postop. Range of Motion (deg)			Durat. of Follow-up (mo)
Function	Pain	Ext.	Flex.	Flex.-Ext. Arc	Function	Pain	Ext.	Flex.	Flex.-Ext. Arc
1	L	M, 65	Flex. contract., stiffness, patellar osteolysis	PTA	50	23	25	90	65	Autograft	Peripatellar fibrotic tissue	80	65	5	115	110	55
2	L	F, 60	Knee instabil., patellar malposition with maltracking and polyethylene wear	OA	35	36	0	105	105	Autograft	Peripatellar fibrotic tissue	93	90	0	115	115	49
3	R	F, 64	Polyethylene wear, osteolysis	OA	18	40	15	40	25	Allograft	Fascia lata	93	90	0	90	90	42
	L	F, 64	Polyethylene wear, osteolysis	OA	26	40	10	90	80	Allograft	Fascia lata	93	90	0	90	90	37
4	L	F, 76	Polyethylene wear, osteolysis	OA	45	31	0	90	90	Autograft	Peripatellar fibrotic tissue	98	100	0	115	115	31
5	R	M, 74	Polyethylene wear, osteolysis	OA	47	40	0	60	60	Allograft	Fascia lata	89	80	0	95	95	30
6	L	M, 45	Polyethylene wear, osteolysis	PTA	24	50	0	90	90	Allograft	Suprapatellar free tissue	88	80	0	90	90	36
7	L	M, 75	Polyethylene wear, osteolysis	OA	82	80	5	90	85	Allograft	Suprapatellar free tissue	93	90	0	90	90	26
8	L	M, 68	Aseptic loosening of femur, tibia, patella	OA	25	20	5	90	85	Autograft	Peripatellar fibrotic tissue	92	70	5	90	85	24