Abstract
We describe a novel hamstring harvesting technique using the “Rule of Twos” as an aide-memoire to dissect the conjoint tendon in an Asian population undergoing anterior cruciate ligament reconstruction.
In a prospective study performed on 17 patients to validate this technique, a 2cm incision is placed 2cm distal and medial to the tip of the tibial tubercle. The surgeon then measured the following variables and calculated their means: 1) Distance from the tip of the tibial tuberosity to the proximal edge of the conjoint tendon (19.4 ± 1.4mm), 2) Width of the conjoint tendon insertion (18.8 ± 1.0mm), 3) Conjoint tendon length (20.1 ± 1.0mm).
Keywords: Hamstring harvest, Anterior cruciate ligament reconstruction, Surgical techniques
1. Introduction
Autologous hamstring grafts, consisting of the gracilis and semitendinosus tendons, are a popular source for reconstructive procedures around the knee. It is especially popular in the reconstruction of anterior cruciate ligament (ACL) injuries with three times greater tensile strength than the native ACL1 and good reported outcomes.2 It is fast replacing the bone-patella tendon-bone (BPTB) autograft as the gold standard in ACL reconstruction due to its lower complication rate, in particular anterior knee pain3 and extension deficit.4
The anatomy of the hamstring tendon has been well described in a study by Charalambous et al.5 The semitendinosus, gracilis and sartorius converge in a common insertion into the anteromedial aspect of the tibia termed the pes anserinus6 with the insertion of the gracilis superior to that of the semitendinosus. This insertion lies 19mm (range 10–25mm) distal and 22.5mm (range 13–30mm) medial to the apex of the tibial tuberosity.7 Despite being separate structures proximally, the gracilis and semitendinosus converge prior to their tibial insertion, described as being 22±7mm distal and 45±6mm medial to the tibial tuberosity.8 The width of the hamstring tendons has been studied extensively by LaPrade et al.9 with the gracilis measuring 8.4mm (range 6.2–11.4mm) and the semitendinosus measuring 11.3mm (range 7.5mm–15.8mm), echoing the findings by Lee et al.10
Despite the popularity of hamstring graft, some authors have noted the challenges of identifying the tendons purely via the anterior incision, prompting Prodromos et al.11 to develop supplementary posterior incisions to aid the identification of the separate tendons. Hamstring harvesting is also not a completely benign procedure and improper techniques may lead to complications such as saphenous nerve injury12 and medial collateral ligament damage.13
In addition, there is no consensus in literature with respect to the incision and anatomical landmarks used in hamstring harvesting, making it difficult for the trainee surgeon to practise a consistent, evidence-based technique. Friedmann14 described a vertical incision located 1 inch medial and 3 inches distal to the tibial tuberosity while Brown et al.15 favoured an oblique incision along the skin creases parallel to the pes anserinus. Marder et al.16 expanded on this concept, siting an oblique incision 3 finger breadths below the medial joint line to facilitate tendon identification.
The senior author of this study has developed a consistent hamstring graft harvesting technique, facilitated by an aide-memoire, “The Rule of Twos”, which makes the process of tendon identification easier, especially for trainee surgeons. This technique has a sound anatomical basis and incorporates findings from more recent anatomical studies.
The aim is thus to evaluate the consistency of this technique and document its complications in a population of patients undergoing hamstring graft harvesting for ACL reconstruction.
2. Methods
Between Jan 2017 and June 2017, skeletally mature patients who underwent primary ACL reconstruction with hamstring grafts by a single, fellowship-trained sports surgeon were recruited for the prospective observational study. The age, gender, height and weight of all patients were recorded. In all patients, an anterior incision was used for graft harvesting with the following measurements recorded: 1) Distance from the tip of the tibial tuberosity to the proximal edge of the conjoint tendon (TTD), 2) Width of the insertion of the conjoint tendon (CTW), 3) Length of the conjoint tendon (CTL). All measurements were made by the same senior surgeon (A.H.T.) after careful dissection of the structures to avoid interobserver error. Distances measured were straight-line distances and could not take into account osseous prominences or depressions. Measurements were reported to the midpoint of a structure's attachment site and osseous landmarks and reported as averages. Progress notes and operative notes of all patients were reviewed to detect any graft harvesting complications. The study was conducted in compliance with the ethical standards described by Padulo et al.17
2.1. Surgical technique
This technique emphasizes on the “Rule of Twos” to enhance the memorability of the technique and increase the adoption of its use by trainee orthopaedic surgeons. Patients were positioned in a supine position with tourniquet inflated and knee flexed to aid exposure. Skin marking is made 1 fingerbreadth below the tibial tuberosity (approximately 2cm distal) and at the mid-point between anterior tibial crest and posteromedial border of tibia (approximately 2cm medial to tibial tuberosity) as shown in Fig. 1. The sartorius fascia is then incised parallel and mid-way between the 2 hamstring tendons identified on palpation. The width of the conjoint tendon is noted to be approximately 2cm and traced 2cm proximally to where the tendons are separate. The fascial bands of the semitendinosus to the medial gastrocnemius were cut under direct vision. The tibial attachment of the conjoint tendon was then sharply divided with a scalpel and a tendon stripper used to harvest the gracilis and semitendinosus tendons in sequence, after ensuring that they were circumferentially freed of all fascial bands.
Fig. 1.
Incision.
3. Results
14 (82.4%) male and 3 (17.6%) female patients were recruited for this study. The biodata of the patients is described in Table 1.
Table 1.
Patient biodata.
| Mean | Standard Deviation | |
|---|---|---|
| Age (years) | 29.8 | 8.0 |
| Height (mm) | 169.5 | 6.7 |
| Weight (kg) | 73.4 | 12.7 |
| BMI (kg/m2) | 25.6 | 4.4 |
The harvested semitendinosus and gracilis tendons were each doubled to create a quadruple graft. There was one case where the gracilis tendon was found to be short and thus a quadruple semitendinosus graft was used instead. The “Rule of Twos” enabled successful identification and harvest of the hamstring tendons in all patients. Measurement of the graft size diameter was performed via a calibrated graft passer and finding a diameter that allowed smooth but firm passage of the quadrupled hamstring graft. The measurements of the graft size, TTD, CTW and CTL is reflected in Table 2. The CTW, CTL and TTD is also represented in the clinical photograph in Fig. 2, Fig. 3, Fig. 4 respectively. No complications of premature graft amputation, saphenous nerve injury or medial collateral ligament injury were noted in our patients.
Table 2.
Hamstring graft measurements.
| Mean | Standard Deviation | |
|---|---|---|
| Graft diameter (mm) | 8.1 | 0.9 |
| TTD (mm) | 19.4 | 1.4 |
| CTW (mm) | 18.8 | 1.0 |
| CTL (mm) | 20.1 | 1.0 |
Fig. 2.
CTW measurement.
Fig. 3.
CTL measurement.
Fig. 4.
TTD measurement.
4. Discussion
This study has demonstrated the consistency and safety of the “Rule of Twos” technique in the localization of the hamstring tendons. The measurements also correlated well with recent cadaveric anatomic studies.
The tibial tuberosity, anterior tibial crest and posteromedial border of the tibia are all consistent bony landmarks that are easily palpated in patients of varying statures and serve as ideal guides to the skin incision. Placement of a 2cm incision, starting 2cm distal and medial to the tibial tuberosity, enabled sufficient exposure of the pes anserinus insertion, in concordance with anatomical studies by Pagnani et al.7 The length of the incision is also sufficient to expose the entire width of the conjoint tendon measuring 18.8 ± 1.0 mm and prevent unnecessary pressure on the skin from excessive retraction. In a systematic fashion, the conjoint tendon can then be traced 20.1 ± 1.0 mm proximally to its bifurcation point and divided safely. This landmark has previously been described relative to the tibial tuberosity8, however the authors feel that describing the length of the conjoint tendon is technically useful as it helps the trainee surgeon trace the bifurcation point from the dissected pes anserinus insertion.
The advantages of this technique are primarily that it is easy to remember and implement. The previously described bony landmarks are readily palpable allowing for easy skin marking, unlike palpating the hamstring tendons for skin marking, especially in patients with thick subcutaneous tissues over the pes anserinus. In addition, the incision is based on existing anatomical studies which provide the basis for a consistent and highly reproducible technique. For greater accuracy, a readily available surgical ruler may be used intra-operatively.
This is a prospective, technical study designed to describe and validate the consistency of the “Rule of Twos” technique in a pilot patient population. The authors acknowledge several limitations. Firstly, the sample size, while sufficient to allow a descriptive study of the technique, may not be sufficiently powered to capture patients with aberrant anatomy or detect rare complications such as saphenous nerve injury. Indeed, patients with variations in hamstring anatomy exist18 but may be rare and require future case studies to highlight these aberrations. Secondly, the patient population is predominantly Asian and the generalization of the study results to other populations may be limited and require future studies.
5. Conclusion
The study has described a novel “Rule of Twos” technique as a useful aide-memoire in the localization of incision in hamstring harvesting, as well as in identifying the width and proximal extent of the conjoint tendon. The results demonstrate the consistency and safety of the technique in an Asian population. It is hoped that this technique can aid surgeons in the safe, reproducible harvesting of hamstring tendons via an easily recalled technique with a sound anatomical basis.
Funding
This study did not receive any specific grant from funding agencies in the public, commercial or not-for-profit sectors.
Declaration of competing interest
None.
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