Combined ACL ALL reconstruction: 1 vs 2-strand outcomes

This Study Highlight reviews a retrospective, propensity score matched paper in Journal of Experimental Orthopaedics that compared two surgical variants used to add an anterolateral ligament (ALL) procedure alongside primary ACL reconstruction. The authors focused on whether technique details (a 1-strand vs 2-strand “back-and-forth” approach) translate into measurable differences in knee laxity and patient outcomes at short to midterm follow-up. For clinicians who routinely follow athletes after surgery, the study is also a practical reminder of how objective laxity measurement can complement clinical grading and patient-reported outcomes in combined ACL ALL reconstruction.

Study question in combined ACL ALL reconstruction

The purpose was to compare post-operative knee laxity and clinical outcomes after ACL plus ALL reconstruction performed with hamstring grafts using either:
(1) a 2-strand back-and-forth technique through two tibial tunnels, or
(2) a 1-strand technique using a single tibial tunnel for the ALL portion.

The authors hypothesized that outcomes would be similar between techniques, despite differences in tunnel strategy and graft handling.

Design and patient population

This was a single-center retrospective comparison of consecutive cases performed between January 2020 and December 2022. The unmatched surgical series included 348 knees treated with the 2-strand approach and 130 knees treated with the 1-strand approach.

Propensity score matching (1:1 nearest-neighbor, caliper 0.01) was used to create two comparable cohorts based on age, sex, BMI, time from injury to surgery, and pre-operative Lysholm and Tegner scores. After matching, there were 70 patients per group; post-operatively, 18 patients were lost to follow-up and 5 underwent revision due to retear (3 in the 2-strand group and 2 in the 1-strand group). The final analyzed cohorts were 58 and 59 patients, respectively. This matching framework aimed to reduce baseline differences when interpreting midterm outcomes in combined ACL ALL reconstruction.

Surgical techniques compared

Both groups underwent ACL reconstruction using hamstring graft constructs described as (3 semitendinosus + 1 gracilis) for the ACL, with gracilis used for the ALL. No cartilage procedures were performed.

What differs in combined ACL ALL reconstruction

In the 2-strand technique (based on a previously published approach), the semitendinosus and gracilis were harvested and left pedicled (tibial insertion preserved), and the ALL reconstruction used two tibial tunnel drill holes (proximal and distal) to create the “back-and-forth” strand configuration.

In the 1-strand technique (adapted from Coulet et al.), the semitendinosus and gracilis tibial insertions were detached, and a single tibial tunnel was used for the ALL reconstruction, which the authors describe as potentially simpler (fewer tunnels) and more aesthetic due to graft palpability under the skin.

Key findings: laxity, PROs, and retear

Follow-up was reported as a mean of 2.4 ± 0.4 years in the 2-strand group and 2.6 ± 0.9 years in the 1-strand group (no statistically significant difference reported).

Objective laxity was assessed post-operatively using Dyneelax measurements of side-to-side (ipsilateral minus contralateral) differential laxity in anterior translation (AT, mm) and internal rotation (IR, degrees). The study reported:

– Differential AT: 0.1 ± 1.3 mm (2-strand) vs 0.4 ± 1.4 mm (1-strand), p = 0.231

– Differential IR: -0.5° ± 2.7 (2-strand) vs -1.1° ± 2.6 (1-strand), p = 0.214

Clinical exam grades also did not differ significantly between groups (post-operative Lachman grade p = 0.302; pivot shift or “jerk test” p = 0.271).

Patient-reported outcomes were similarly comparable between techniques at follow-up:

– KOOS-12: 41.7 ± 5.6 vs 42.3 ± 5.9 (p = 0.209)

– Lysholm: 89.4 ± 9.0 vs 88.5 ± 11.0 (p = 0.954)

– ACL-RSI: 75.5 ± 19.0 vs 78.5 ± 19.0 (p = 0.318)

Tegner distributions were reported without a statistically significant difference (p = 0.246). Retears requiring revision occurred in 3 matched patients in the 2-strand group and 2 in the 1-strand group, with no significant difference stated by the authors. Overall, the results suggest technique choice did not materially change midterm stability or function in combined ACL ALL reconstruction.

Clinical interpretation

From a practical perspective, this study supports the idea that surgeons may be able to choose the 1-strand or 2-strand approach based on technical preference (for example, number of tibial tunnels and ease of drilling) without expecting large differences in measured laxity or commonly used outcome scores at around 2 to 3 years.

The authors also note an observation that mean post-operative internal rotation was reduced compared to the contralateral knee (negative differential IR values). While reduced IR may theoretically be protective for graft survival in the short to midterm, the paper appropriately raises a caution: longer-term effects on the lateral compartment (cartilage stress or wear) were not assessed in a way that can answer that question here. This is especially relevant when counseling more lax patients and monitoring results over time after combined ACL ALL reconstruction.

Where objective laxity testing fits

The central clinical question in this paper was not only “how do patients feel?” but also “how stable is the knee?” The authors therefore paired clinical tests (Lachman and pivot shift) with an objective device-based assessment of side-to-side laxity using the Dyneelax arthrometer. That matters because clinical grading can be influenced by examiner technique, guarding, and patient habitus, and because subtle differences in rotational or anterior laxity may be difficult to quantify consistently without instrumentation.

In day-to-day follow-up, objective laxity data can help contextualize symptoms and functional progression, particularly when patients report instability despite reassuring strength testing or acceptable patient-reported outcome scores. Device-based measurements can also support comparisons between surgical variants, rehab protocols, or return-to-sport timelines in combined ACL ALL reconstruction. Importantly, arthrometer testing complements, but does not replace, MRI and clinical examination when evaluating suspected retear, graft elongation, new meniscal injury, or other intra-articular pathology.

If you are standardizing your measurement approach across visits, see the background on the Dyneelax knee arthrometer (the device type used in this study) and, for anterior laxity assessment workflows commonly used in ACL practice, the GNRB arthrometer.

Study limitations and what we cannot verify

Several limitations in the PDF affect how confidently these findings can be generalized. The study is retrospective and, even with propensity score matching, residual confounding is likely. Matching did not account for all potentially influential pre-operative variables (the authors explicitly mention items such as meniscal injury and pre-operative laxity measures).

Pre-operative laxity was not measured objectively with an arthrometer, so the magnitude of improvement from pre-op to post-op cannot be quantified or compared between techniques. Tunnel placement was not analyzed, which may matter for long-term biomechanics. In addition, follow-up is short to midterm, and the paper itself calls for longer-term evaluation related to reduced internal rotation and potential lateral compartment effects.

Finally, the provided PDF does not include enough detail to verify certain potentially relevant clinical subgroups (for example, detailed tear patterns, repair techniques, or cartilage status across groups) beyond what the authors summarized.

Key takeaways

• At a mean follow-up of about 2 to 3 years, the 1-strand and 2-strand techniques showed no significant differences in objective AT or IR laxity, clinical grades, or common patient-reported scores.
• Retears requiring revision were reported in both groups (3 vs 2 in the matched cohorts), with no significant difference stated.
• For surgeons considering technical trade-offs (one tibial tunnel vs two), the findings suggest similar midterm stability and function in combined ACL ALL reconstruction.
• Objective arthrometer testing (as used here) can strengthen follow-up by adding quantifiable side-to-side laxity data alongside clinical exam and MRI, especially when symptoms and exam do not fully align.