Variations in functional outcome based on hamstring autograft thickness estimated using transportal technique in arthroscopic anterior cruciate ligament reconstruction

INTRODUCTION

The arthroscopic anterior cruciate ligament reconstruction (ACLR) is one of the most common surgeries in orthopedic surgery done for complete anterior cruciate ligament (ACL) tears.^[1] Several studies have also shown that autograft and allograft (patellar tendon, hamstring tendon, tibialis anterior, and Achilles tendons) may successfully reconstruct the ACL.^[2,3] However, no convincing data currently exist regarding recent trends for the appropriate thickness of the graft to be used, especially in the Indian subcontinent. Adequate thickness of the graft for a primary ACLR determines the functional and morbidity status following the surgery, thereby providing better outcomes in the ACL deficient knees. The study’s major goal is to assess the average anterior-posterior diameter (APD) of the tibial footprint during arthroscopic ACLR and its functional outcome to determine optimum graft thickness using a transportal technique.

MATERIALS AND METHODS

Interventions

The anteromedial and anterolateral portals were made and diagnostic examination of the knee was done to diagnose any associated injury to the knee. The ACL footprint was identified and remnants were removed from the tibial notch. The APD of the tibial footprint of ACL is measured using an arthroscopic ruler through transportal [Figures 1 and 2]. The gracilis and semitendinosus tendons were harvested and prepared. The ideal graft thickness of more than 70% of the tibial footprint APD was adhered to in all the cases.

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Figure 1:

Arthroscopic ruler.

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Figure 2:

(a) The anteroposterior diameter of the tibial footprint of the anterior cruciate ligament is measured using (b) an arthroscopic ruler.

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The femoral footprint has marked at the center with an awl. The anatomical femoral and tibial tunnels were prepared meticulously to prevent non-anatomical tunnel placements in both coronal and sagittal planes. We used a fixed loop device and the graft was fixed to the femur. Following that, repeated flexing-extending cycles of the knee were done to pre-install the graft. The tibial fixation was done with an ideal amount of tension using absorbable interference screws. After performing ACL reconstruction, other minor Grade-1 and 2 meniscal tears were identified and conservative management was carried out accordingly.

RESULTS

DISCUSSION

ACLR with the hamstring tendon has become a common and most preferred tendon graft for surgeons and it has shown itself to be efficient inadequately selected individuals.^[4] A good functional outcome depends on graft size, tunnel position, fixation methods, treatment of associated lesions, and proper rehabilitation after surgery. Biomechanically, both hamstring and bone patellar tendon bone graft show similar properties.^[5] We used absorbable interference screws for graft fixation in all our cases. Several recent meta-analyses and network meta-analyses have demonstrated a similar functional outcomes in the fixation methods.^[6,7]

We studied the variance in the functional outcome of autograft thickness at the tibial footprint measured using an arthroscopic ruler through an arthroscopic trans-portal approach during ACLR. The femoral footprint occupies 70% of the area compared to tibial insertion and the substance of ACL constitutes only about 50% of tibial insertion. This shows that the tibial insertion footprint is the single most important measurement required for pre-operative planning of individualized ACLR.^[8,9]

The APD of the tibial footprint aids in determining the graft’s adequacy and the ideal thickness of the graft to be placed should be >70% of the tibial footprint APD^[10] and it is one of the important components to regain a functionally stable knee joint. Furthermore, an inadequate graft size may result in graft failure. However, the literature on the autograft thickness on the functional outcome is rare. Hence, we studied the difference in functional outcome in ACLR autograft thickness between graft thickness >85% and graft thickness ≤85%.

Studies have shown that revision surgery is more common among grafts with a diameter of 7 mm or less.^[11,12] According to Spragg et al.,^[11] the patients that required revision surgery more often with the graft thickness falling between 7.0 and 7.5 mm on the lesser side. Mariscalco et al.^[12] state that an inadequate graft size is directly proportional to poor functional score and increased revision rate. Treme et al.^[13] proposed that the graft diameter of <7 mm will have a higher risk of failure. Conte et al.^[14] state that the ACLR using hamstring autograft with a diameter 8 mm or more increases the success rates compared to graft diameter <8 mm. Howe et al.^[15] reported that 96% patients were content with their functional results, while only 4% patients had unsatisfied results in their long-term follow-up.

Similarly, Chen et al.^[16] reported to have normal or nearly normal IKDC scores in 91% patients undergoing ACL surgery. Khajotia et al.^[17] recorded a mean graft diameter of 8.24 mm from their study and the IKDC score was normal in 84% of patients and only 26% of patients had an abnormal score. Chodavarapu et al.^[18] state that with a mean graft diameter of 7.9 mm that 84% of patients regained pre-injury level activity. The post-operative IDKC scores were 0–60 in 72% patients and 24% patients had a score at 60–70.

The mean IKDC scores of patients with graft thickness ≤85% were insignificantly higher than graft thickness >85% at 3^rd post-operative month, but the scores of patients with graft thickness >85% were insignificantly higher than graft thickness ≤85% in the 6^th postoperative month. However, the IDKC score difference was statistically higher for graft thickness >85% than graft thickness >85% at the 12^th postoperative month. The mean KSS scores of patients with graft thickness >85% were insignificantly higher compared to graft thickness ≤85% at 3^rd and 6^th post-operative months. However, the KSS score difference was statistically higher for graft thickness >85% than graft thickness >85% at the 12^th post-operative month.

Hence, both the IDKC and KSS scores were better for graft thickness >85% compared to graft thickness ≤85% at the early post-operative months with a statically significant better scores for graft thickness >85% at 12^th post-operative month. From our study, we can say that the functional outcomes were better for patients with graft thickness more than or equal to 85%.

Confounding factors of this study are anatomical femoral tunnel placements, femoral tunnel diameter, graft bending angle, and graft fixation methods.^[19] The post-operative stiffness, instability, infection, arthrofibrosis, complex regional pain syndrome, and synovitis were the common complications^[20] and were not recorded in our study. Clinically, studies comparing different hamstring and quadriceps tendon graft preparations, thickness, and fixation are needed. Larger comparative studies are also needed to validate the results for the specific study populations. Finally, the current literature lacks long-term follow-up studies and higher level of evidence studies is also needed.

CONCLUSION

Our study evaluated the relationship between ACL graft APD thickness and patient-reported functional outcome scores, which was done rarely in the literature. We conclude from our study that the patients with graft thickness more than 85% of tibial AP footprint had better short-term functional outcome and a significant long-term outcome at 12^th post-operative month compared to patients with ≤85% graft thickness in arthroscopic ACL reconstruction using transportal approach.