Autograft Choice in Anterior: Cruciate Ligament Reconstruction Should It Be Patellar Tendon or Hamstring Tendon?

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Chapter 93 Autograft Choice in Anterior: Cruciate Ligament Reconstruction Should It Be Patellar Tendon or Hamstring Tendon?

DANIEL. WHELAN, MD, MSc, FRCS(C), KATIE N. DAINTY, MSc, CRPC, DENISE. CHAN, BSc, MBT, NICHOLAS G. MOHTADI, MSc

The optimal graft choice for reconstruction of the deficient anterior cruciate ligament (ACL) remains controversial. Graft options currently in use include autogenous or autologous patellar tendon, ipsilateral patellar tendon, hamstring tendons (double or quadruple strand), quadriceps tendon (with or without patellar bone), xenografts, and synthetic replacements or augmentations. Autograft tissue currently is the most common source for grafts worldwide, with the main choices being the patellar tendon and hamstring tendons (semitendinosus and gracilis). The advantages and disadvantages of both these popular autografts have been discussed extensively in the literature. Both the quadruple-strand hamstring and bone patellar tendon grafts have demonstrated more than adequate load to failure and single pull strengths with multiple fixation configurations when biomechanically compared with native ACLs.¹^–³ Patellar tendon grafts have traditionally been favored for their robust strength, relative ease of operative fixation, and the potential for bone-to-bone ingrowth after implantation. Hamstring tendons are a relatively newer graft choice and have become popular for the relative ease and low morbidity of their harvest.

In the clinical research realm, most early investigations of ACL reconstruction were retrospective case series using a single graft or comparative retrospective cohorts. Such observational data were prone to the limitations of bias and confounding. More recently, however, several randomized trials have been published comparing outcomes.

Because of the dramatic increase in published trials on ACL graft choice in the last 4 years, a systematic review of published randomized, Level I evidence was undertaken. The objective in writing this chapter was to synthesize this evidence, in a narrative fashion, to obtain inference with respect to graft rerupture, postreconstruction laxity, and incidence of complications after ACL reconstruction with either bone–patellar tendon–bone (BPTB) or quadruple-strand hamstring autografts.

A comprehensive search of electronic publication databases (MEDLINE, EMBASE, and the Cochrane Central Register of Controlled Trials) was done to identify relevant studies. Bibliographies from relevant publications found electronically were hand-examined for further potential inclusions. A title review was also done for presentations and posters in the proceedings of three major orthopedic meetings (the American Academy of Orthopaedic Surgery, the International Society of Arthroscopy, Knee Surgery and Orthopaedic Sports Medicine, and the Canadian Orthopaedic Association).

Eighteen studies were identified by the search criteria as prospective, randomized comparisons with patients being allocated to receive one of the two specified autografts. Seven of these were subsequently excluded because group assignment was not specified as being strictly by random allocation (birth date/year randomization was accepted, however, because this did not have the potential for manipulation).⁴^–¹⁰ Three investigations were further eliminated because they used two-strand hamstring grafts (versus four).¹¹^–¹³ One investigation reported outcome data recorded at 12 months (vs. 24 months).¹⁴ Another study utilized a novel hamstring graft preparation (including a bone block) that was not believed to be a standard technique.¹⁵ The remaining six investigations met the full criteria for eligibility and were included in the final analysis.¹⁶^–²¹

The cumulative sample from the 6 investigations was 483 patients, 235 having received BPTB grafts and 248 having received quadruple-strand hamstring grafts. The studies typically included patients of similar age ranges (14–59 years). None of the studies included skeletally immature patients. The sex distribution favored male individuals. The proportion of acute (<3 months) versus chronic ACL injuries was difficult to determine from the information provided in each study, as was the presence of associated meniscal, chondral, or ligamentous pathology at the time of reconstruction.

TECHNICAL CONSIDERATIONS

The majority of the studies used “aperture fixation” with interference screws for graft fixation on both the femoral and tibial sides of the joint. Metal screws were the preferred fixation for both grafts in the earlier studies, with a trend to bioabsorbable screws for fixation of soft-tissue grafts in more recent investigations. Two studies used extracortical fixation with either plate or endobutton (Smith & Nephew, Andover, Massachusetts, USA) fixation on the femoral side for hamstring grafts.^17,¹⁸ Maletis and coworkers¹⁹ used bioabsorbable screws on both the femoral and tibial sides; this is the only study to use identical fixation for both grafts. None of the studies specified the tension at which the grafts were fixed. The flexion angle of the knee at the time of fixation was inconsistently reported and varied from hyperextension to up to 70 degrees of flexion. Rehabilitation protocols were similar, as were follow-up schedules.

JOINT LAXITY

All reconstructions were performed endoscopically through single tibial incisions. Instrumented laxity measurements utilizing the KT-1000 arthrometer were common to all 6 studies; however, the forces at which the knees were tested (89 vs. 134 N vs. maximum manual) and the method of reporting (side-to-side difference vs. proportion of patients with mild/moderate/gross laxity) varied. Despite these differences, no statistically significant differences in terms of instrumented laxity between the 2 grafts were found in any of the individual studies. A trend existed toward increased side-to-side laxity with hamstring tendon grafts in all 6 studies; however, the differences were often small (<3 mm) and of uncertain clinical significance.

CLINICAL OUTCOMES

Strength and range of motion were inconsistently reported among the studies. Although early follow-up (<1 year) often demonstrated strength differences, no consistent trends were noted across the studies for either graft in terms of flexion and extension strength at 2 years after reconstruction. Maletis and coworkers ¹⁹ found persistent flexion weakness in the hamstring group and persistent quadriceps weakness in the patellar tendon group, but the deficits were small and of uncertain clinical significance. Similarly, although extension deficits were seen early in the BPTB group in several studies, the groups usually equilibrated at 2-year follow-up. In 2 studies, the extension deficit persisted.^17,²⁰

Two studies demonstrated a statistically significant proportion of patients in the hamstring group with an abnormal pivot shift examination at final follow-up.^17,¹⁹ The severity of the pivot shift (i.e., a “glide” vs. an overt subluxation) was specified in only 1 study, and no patients demonstrated more than a grade 1 (glide).¹⁹ No differences were found between the grafts with respect to the one-leg hop test in the studies that reported this outcome.

FUNCTIONAL OUTCOMES

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