1. The Journal of Arthroplasty Vol. 23 No. 8 2008
Management of Extensor Mechanism Deficit as a
Consequence of Patellar Tendon Loss in
Total Knee Arthroplasty
A New Surgical Technique
Rajesh Malhotra, MS (Orthopedics), Bhavuk Garg, MS (Orthopedics),
Vivek Logani, MS (Orthopedics), and Surya Bhan, MS (Orthopedics), FRCS
Abstract: Extensor mechanism disruption is an uncommon but devastating
complication of total knee arthroplasty. A new technique of extensor mechanism
reconstruction for patellar tendon loss, after total knee arthroplasty, with the help of
extensor mechanism composite allograft is described. Four patients with chronic
extensor mechanism–deficient total knee arthroplasty were undertaken for revision
surgery along with reconstruction of extensor mechanism with an innovative
technique using an extensor mechanism composite allograft consisting of a patella–
patellar tendon–tibial tubercle. On final follow-up, none of the patients had extensor
lag but for 10° of extensor lag in 1 patient only. Providing an environment for bone-
to-bone healing both proximally as well as distally and supervised postoperative
rehabilitation led to encouraging results in the management of a failed extensor
mechanism after total knee arthroplasty. Key words: extensor mechanism, total
knee arthroplasty, allograft, extensor mechanism composite allograft.
© 2008 Elsevier Inc. All rights reserved.
Extensor mechanism disruption is an uncommon A unique solution to this problem of chronic
yet devastating complication of total knee arthro- extensor mechanism rupture/deficiency is recon-
plasty. Its prevalence is 0.17% to 2.5% [1,2]. The struction with the help of an extensor mechanism
problem seems multifactorial [3], and a spectrum of allograft. A fresh-frozen or freeze-dried allograft
surgical procedures ranging from direct repair of the consisting of quadriceps tendon, patella, patellar
acute rupture [4,5] to the reconstruction of a tendon, and tibial tubercle is used as promoted by
chronically deficient extensor mechanism has been Emerson, Jr, et al [6,7]. Although the early clinical
recounted [6,7]. results were promising, further follow-up revealed
that an extensor lag of 20° to 40° had developed in 3
of the 9 knees. The preceding technique was
modified by Nazarian and Booth, Jr [8], so that the
From the Department of Orthopaedics, All India Institute of Medical allograft be tightly tensioned in full extension.
Sciences, New Delhi, India. All the aforementioned techniques bank on soft
Submitted March 9, 2007; accepted August 8, 2007. tissue–to–soft tissue healing and have reported
No benefits or funds were received in support of the study.
Reprint requests: Rajesh Malhotra, MS (Orthopedics), Depart- attenuation of host donor junction, particularly at
ment of Orthopaedics, All India Institute of Medical Sciences, the proximal host donor quadriceps junction, as the
New Delhi, India. most common complication, resulting in poor out-
© 2008 Elsevier Inc. All rights reserved.
0883-5403/08/2308-0009$34.00/0 come of these procedures. We describe an innovative
doi:10.1016/j.arth.2007.08.011 technique of extensor mechanism reconstruction
1146

2. Management of Extensor Mechanism Deficit as a Consequence of Patellar Tendon Loss Malhotra et al 1147
Table 1. Clinical and Demographic Data
Patient 1 2 3 4
Age (y) 68 71 63 69
Sex Male Female Female Female
Extensor lag (degrees) 40 45 40 30
Other clinical findings Genu recurvatum Genu recurvatum Valgus laxity of 15°, genu recurvatum Genu recurvatum
Associated medical comorbidities Obese, hypertensive Rheumatoid arthritis Obese, hypothyroid, hypertensive Diabetic
Prior surgical treatment Primary repair Primary repair Primary repair followed by Primary repair
augmentation with semitendinosus
Postulated cause of patellar Extensive release Extensive release Distal realignment with lateral release Difficult exposure
tendon rupture
with patella–patellar tendon–tibial tubercle allograft augmentation with tendon grafts, was discussed
counting exclusively on extrapolative bone-to-bone with all of the patients. None of the patients had
healing, which is more predictable. clinical or laboratory evidence of infection.
On physical examination, the following variables
Materials and Methods were recorded: active and passive range of motion,
presence or absence of extensor lag, extensor
Consecutive reconstructions with extensor mechanism tracking, as well as neurovascular
mechanism allograft in 4 patients (3 women and 1 status. The tracking of the extensor mechanism
man) were under taken by the surgeon (RM) in the during range-of-motion testing was examined clo-
institute. The clinical and demographic data of all 4 sely and was found to be normal. There was no distal
patients are shown in Table 1. neurovascular deficit in any of the patients.
All knees had a failed extensor mechanism All but 1 patient had revision total knee arthro-
associated with a total knee arthroplasty. One plasty at the time of extensor mechanism recon-
patient had a prior failed direct repair and again a struction because of associated aseptic loosening or
failed extensor mechanism repair augmented by component malrotation. Implants were retained,
semitendinosus autograft. The other 3 patients had and the polyethylene was changed in the fourth
failed primary repair. Nonoperative treatment, patient during extensor mechanism reconstruction.
including bracing as well as other operative options, The patients were observed for a mean of
including additional attempt at direct repair and 21 months, ranging from 14 to 30 months. Clinical
Fig. 1. A and B, Intraoperative and schematic diagram showing preparation of donor allograft and creation of ridge on
undersurface of patella.

3. 1148 The Journal of Arthroplasty Vol. 23 No. 8 December 2008
Fig. 2. Intraoperative (A) and schematic diagram (B) showing creation of trough in host patella.
and radiographic examination was performed at 6 remained in the central portion, on either side
and 12 weeks, 6 months, 1 year, and every year of which the cancellous surface was exposed
thereafter. Active and passive range of motion, (Fig. 1A and B).
along with extensor lag, were recorded at an each
follow-up. The knee was graded in accordance with Preparation of Host Patellar Trough
the 100-point system of the Hospital for Special
We divided the host patella in midline long-
Surgery (New York, NY), preoperatively and post-
itudinally and removed some bone on either side
operatively, beginning at 3 months. A score of more
with the help of an oscillating saw to create a trough
than 84 points is considered an excellent result; 70
of a width of 1 cm (Fig. 2A and B). The allograft
to 84 points, a good result; 60 to 69 points, a fair
patella with a ridge created on its articular surface
result; and less than 60 points, a poor result.
was then fitted/fixed into this trough (Fig. 3A and B)
and secured with the help of screws inserted
Surgical Technique
horizontally, going from host bone to allograft to
Allograft Preparation. Simultaneous with the
host bone.
revision or placement of the total knee arthroplasty
components, the patella–patellar tendon–tibial
Preparation of the Host Proximal Tibial Trough
tubercle allograft was prepared on the back table.
We first marked with a marking pen over the tibial We created a trough in the proximal portion of
tubercle and proximal part of the allograft tibia and the tibia as recommended [9,10]. The allograft
planned harvest of the allograft tibial bone block, in tibial tubercle was then inserted into the host tibial
a rectangular fashion. With the use of a small thin trough and was gently press-fit with a bone tamp
microsagittal saw, the allograft block was harvested or punch, in an “up and in” fashion, to lock the
from the allograft tibia, with careful attention so as graft in place. This graft was then secured with the
not to damage the allograft patellar tendon. help of wires. Once the allograft was secured,
Next, we cut the articular portion of patella in extensor mechanism tracking and strength was
such a way that a longitudinal ridge of bone checked and was found satisfactory.
Fig. 3. Intraoperative (A) and schematic diagram (B) showing securing of allograft proximally.

4. Management of Extensor Mechanism Deficit as a Consequence of Patellar Tendon Loss Malhotra et al 1149
Table 2. Follow-up, Range of Motion, and Knee Scores
Follow-up Preoperative ROM Postoperative ROM Preoperative Knee Postoperative Knee
Patient (mo) (Degrees) (Degrees) Score Score
1 30 40-90 0-100 21 88
2 24 45-100 10-90 18 76
3 14 40-110 0-100 27 68
4 16 30-100 0-90 22 84
ROM indicates range of motion.
Postoperative Care and Rehabilitation patients had no extensor lag at their most recent
follow-up. The mean knee score at the time of the
In the operating room, the limb was placed in full
latest follow-up was 79 points (range, 68 to 88
extension in a plaster slab. The patients were given
points). Radiographic analysis showed all allografts
a knee brace in extension after wound inspection at
to be incorporated proximally as well as distally by
3 days. Patients were maintained with the knee in
12 months.
full extension for 8 weeks after surgery. During this
The results are depicted in Table 2. Postoperative
period, we allowed touch-down weight-bearing
range of motion and x-rays of 1 patient are shown in
only. Isometric static quadriceps contractions were
Figs. 4 and 5.
encouraged. At 6 weeks, patients were advanced
At their recent follow-up, all but 1 patient were
to weight-bearing as tolerated. During weight-
able to walk without an assistive device. One patient
bearing, we locked the brace in full extension. At
had a superficial wound infection, which was
12 weeks, we allowed further active flexion up to a
controlled by intravenous antibiotics. No other
maximum of 90°, and gentle quadriceps strength-
complications were seen.
ening exercises were initiated. Passive flexion was
not permitted, to minimize the chance of graft
failure and early attenuation. Postoperative x-rays
Discussion
were taken at each follow-up for the evaluation of
the incorporation of allograft bone proximally as
The extensor mechanism seems to play a crucial
well as distally.
role in primary as well as revision total knee
arthroplasty. The prevalence of complications
Results related to the extensor mechanism in total knee
arthroplasty is around 4% [2,9,10]. Patellar
One patient had an associated valgus laxity of 15° maltracking; patella alta/baja; abnormal patellar
as well as a 10° extensor lag. The valgus laxity was wear; patellar subluxation/dislocation; and disrup-
treated with a medial collateral ligament reconstruc- tion of extensor mechanism caused by patella
tion using the semitendinosus. The remaining 3 fracture, quadriceps tendon rupture, and patellar
Fig. 4. Postoperative active range of motion at 24 months.

5. 1150 The Journal of Arthroplasty Vol. 23 No. 8 December 2008
appearance, weakness of ankle plantar flexion,
and residual extensor lag [16]. Augmentation with
xenograft and synthetic carbon fiber implants is
largely unsuccessful [17].
Allograft reconstruction of the extensor mechan-
ism has been debatable. Options for allograft
reconstruction include patellar tendon alone [18],
Achilles tendon allograft, Achilles tendon-calca-
neum composite allograft [19], and extensor
mechanism composite allograft [6,7].
Emerson, Jr, et al [6,7], had reported promising
early results after use of an extensor mechanism
allograft to reconstruct a failed extensor mechanism
in patients with a previous total knee arthroplasty.
Fig. 5. Postoperative x-rays showing good incorporation However, the authors concluded that the long-term
of allograft proximally as well as distally. results needed further evaluation. The original
technique of Emerson, Jr, et al, was modified by
Nazarian and Booth, Jr [8], who tensioned the
tendon rupture, constitute the spectrum of exten- allograft tightly after ensuring full knee extension
sor mechanism complications. before placement of the graft. Intraoperative under-
Patellar tendon rupture is a devastating extensor tensioning of graft and poor graft–soft tissue healing
mechanism complication after total knee arthroplasty. due to poor fibroblastic response, leading to severe
Its incidence has been reported as ranging from 0.17% attenuation of graft host junction, particularly at the
to 2.5% in various series [1,2]. Factors associated with proximal quadriceps junction, has remained a
patellar tendon rupture include a difficult exposure in problem with these techniques [6-8].
a stiff knee, extensive release of the patellar tendon at Our modification of this technique is based on the
the time of surgical exposure, manipulation for the rationale of replacing the incompetent tissue with
treatment of limited motion, revision total knee whole, structurally sound tissue, placing surgical
arthroplasty, and distal realignment of the extensor junctions at the most favorable healing sites possible
mechanism to treat patellar maltracking [11]. To in the well-vascularized environment of proximal
prevent intraoperative rupture, various measures tibial metaphysis and the host patellar cancellous
(namely, lateral release/proximal release; tibial tuber- bone. This technique produces more favorable
cle osteotomy; holding patellar tendon with clamp, healing, particularly at the proximal junction, by
washer, or pin) have been in vogue. Postoperatively providing a bony cancellous bed of the host bone for
aggressive rehabilitation; falls with acute flexion; repair. Durability of the repair was evident from the
remanipulation; and progressive attrition of extensor fact that the repair was holding even at the end of
mechanism due to prosthetic impingement, removal 30 months without any extension lag except in 1
of too much bone from patella, or devascularization patient. This technique, however, is possible only
by surgical process, have also been associated with because we do not routinely resurface the patella and
patellar tendon rupture. had a good host patellar bone stock. In case of poor
The management of a chronically deficient patellar bone stock, we recommend the technique of
extensor mechanism depends upon availability Emerson, Jr, et al [6,7], wherein the extensor
and quality of local tissues, functional demands mechanism is reconstructed by securing the allograft
of the patient, and overall medical status, including with the host quadriceps tendon proximally.
comorbidities. There is no role of conservative In summary, this technique may play a significant
management. Primary repair with wires, staples, or role in the outcome of reconstruction of a chronic
sutures is often unsuccessful [1,12,13]. Augmenta- patellar tendon loss with an extensor mechanism
tion of primary repair with autogenous tissuelike allograft after a total knee arthroplasty. Our method
free fascia lata, plantaris tendon, gracilis tendon, of extensor mechanism reconstruction, which aims
and semitendinosus graft, has also been described, for bone-to-bone healing, is durable and has not
but results are consistently poor [1,13-15]. The use shown deterioration over time. We recommend this
of a medial gastrocnemius flap for reconstruction method for extensor mechanism reconstruction in
has the advantage of providing viable autogenous cases where host patellar bone stock is good. Careful
tissue to cover the anterior-inferior aspect of the attention to graft preparation and handling, provid-
knee but has the disadvantages of a poor cosmetic ing an environment for bone-to-bone healing both

6. Management of Extensor Mechanism Deficit as a Consequence of Patellar Tendon Loss Malhotra et al 1151
proximally as well as distally and supervised post- 9. MacCollum MS, Karpman RR. Complications of the
operative rehabilitation, led to encouraging results PCA anatomic patella. Orthopedics 1989;12:1423.
in the management of a failed extensor mechanism 10. Doolittle KH, Turner RH. Patellofemoral problems
after total knee arthroplasty. However, a more following total knee arthroplasty. Orthop Rev 1988;
17:696.
extensive and long-term study involving more
11. Rand JA. Extensor mechanism complications follow-
patients is needed to authenticate the success in ing total knee arthroplasty. J Bone Joint Surg Am
addressing this complex problem. 2004;86:2062.
12. Grace JN, Rand JA. Patellar instability after total knee
References arthroplasty. Clin Orthop 1988;237:184.
13. Abril JC, Alvarez L, Vallejo JC. Patellar tendon
1. Rand JA, Morrey BF, Bryan RS. Patellar tendon avulsion after total knee arthroplasty. A new techni-
rupture after total knee arthroplasty. Clin Orthop que. J Arthroplasty 1995;10:275.
1989;244:233. 14. Cadambi A, Engh GA. Use of a semitendinosus tendon
2. Lynch AF, Rorabeck CH, Bourne RB. Extensor autogenous graft for rupture of the patellar ligament
mechanism complications following total knee arthro- after total knee arthroplasty. A report of seven cases.
plasty. J Arthroplasty 1987;2:135. J Bone Joint Surg Am 1992;74:974.
3. Parker DA, Dunbar MJ, Rorabeck CH. Extensor 15. Wilson FC, Venters GC. Results of knee replacement
mechanism failure associated with total knee arthro- with the Walldius prosthesis: an interim report. Clin
plasty: prevention and management. J Am Acad Orthop 1976;120:39.
Orthop Surg 2003;11:238. 16. Jaureguito JW, Dubois CM, Smith SR, et al. Medial
4. Ecker ML, Lotke PA, Glazer RM. Late reconstruction gastrocnemius transposition flap for the treatment of
of the patellar tendon. J Bone Joint Surg Am 1979; disruption of the extensor mechanism after total
61:884. knee arthroplasty. J Bone Joint Surg Am 1997;
5. Larsen E, Lund PM. Ruptures of the extensor mechan- 79:866.
ism of the knee joint. Clinical results and patellofemoral 17. Jenkins DH, McKibbin B. The role of flexible carbon-
articulation. Clin Orthop 1986;213:150. fibre implants as tendon and ligament substitutes in
6. Emerson Jr RH, Head WC, Malinin TI. Reconstruction clinical practice. A preliminary report. J Bone Joint
of patellar tendon rupture after total knee arthro- Surg Br 1980;62-B:497.
plasty with an extensor mechanism allograft. Clin 18. Zanotti RM, Freiberg AA, Matthews LS. Use of patellar
Orthop 1990;260:154. allograft to reconstruct a patellar tendon-deficient
7. Emerson Jr RH, Head WC, Malinin TI. Extensor knee after total joint arthroplasty. J Arthroplasty
mechanism reconstruction with an allograft after total 1995;10:271.
knee arthroplasty. Clin Orthop 1994;303:79. 19. Crossett LS, Sinha RK, Sechriest VF, et al. Reconstruc-
8. Nazarian DG, Booth Jr RE. Extensor mechanism tion of a ruptured patellar tendon with Achilles
allografts in total knee arthroplasty. Clin Orthop 1999; tendon allograft following total knee arthroplasty.
367:123. J Bone Joint Surg Am 2002;84:1354.